Also introduce a way to copy a struct or list which applies membranes to all embedded capabilities, since this seems like it will be needed in conjuction with the above.

Update RPC docs for the change to a single bootstrap interface

Update comment: MessageReader::reset() has not existed for a very long time.

Workaround nonexistent EPROTO on OpenBSD

Fixes #221.

**The problem**

The methods MessageReader::initCapTable() and MessageBuilder::getCapTable() always felt rather hacky. initCapTable() in particular feels like something that should be handled by the constructor. However, in practice, the cap table is often initialized based on a table encoded within the message itself. That is, an RPC message contains a "payload" which includes both the application-level message structure and a table of capabilities. The cap table has to be processed first, then initCapTable() is called on the overall message, before the application structure can safely be read.

The really weird part about this is that even though the cap table only applies to one branch of the message (the payload), it is set on the *whole* MessageReader. This implies, for example, that it would be impossible to have a message that contains multiple payloads. We haven't had any need for such a thing, but an implemnetation that has such artificial limitations feels very wrong.

MessageBuilder has similar issues going in the opposite direction.

All of this ugliness potentially gets worse when we introduce "membranes". We want a way to intercept capabilities as they are being read from or written to an RPC payload. Currently, the only plausible way to do that is, again, to apply a transformation to all capabilities in the message. In practice it seems like this would work out OK, but it again feels wrong -- we really want to take a single Reader or Builder and "wrap" it so that transformations are applied on capabilities read/written through it.

**The solution**

This change fixes the problem by adding a new pointer to each struct/list Reader/Builder that tracks the current cap table. So, now a Reader or Builder for a particular sub-object can be "imbued" with a cap table without affecting any other existing Readers/Builders pointing into the same message. The cap table is inherited by child Readers/Builders obtained through the original one.

This approach matches up nicely with membranes, which should make their implementation nice and clean.

This change unfortunately means that Readers and Builders are now bigger, possibly with some performance impact.

Allow trailing commas in parenthesized and bracketed lists.

Fix bug where calling a list setter using a list obtained from a similarly-typed getter, but where the underlying pointer was null, would write an incorrectly-typed pointer in the destination (specifically, an empty List(Void)). Now it sets an empty list of the correct type.

Unfortunately, the layout algorithm had a bug which caused incorrect layout when declaring a union whose lowest-ordinal field was of type Void and nested in an inner union. That is:

    union {
      a :union {
        b @0 :Void
        ...
      }
      ...
    }

In this case, all the fields in the struct after the Void field -- including both unions' discriminants -- would end up misplaced. Although they did not end up overlapping (and therefore the incorrect layout "worked"), the result broke schema evolution rules around "retroactive unionization".

Unfortunately, we must break compatibility with any protocol that happened to contain the above pattern. Luckily, it's a fairly obscure case. Unluckily, Cap'n Proto's own schema format contains such a pattern. Luckily, the use of this pattern was introduced in v0.6.x and therefore has not been in any release build so far.

And add a test to verify this behavior.

.gitignore should not ignore bootstrap files, which are not build artifacts. Possibly related to #216.

Fix problem with some RealmGateway template helpers

It turns out that somehow these templates were missing InternalOwner and
ExternalOwner definitions, which was causing problems if a RealmGateway
was defined with them.

Allow setting dynamic AnyPointer fields with a capability

Don't kill the connection just because someone pipelined on a capability pointer that turned out to be null.

Maybe::emplace() should return the newly-constructed value so that you don't have to immediately KJ_ASSERT_NONNULL it.

Fixed installation of schema files via CMake.

Fix Syntax highlighting for Kate/KDevelop

sed -r is a GNU extension, apparently, and due to stars aligning, this didn't break the build, but led to a totally bogus soname on non-GNU systems. Argh.

Apparently most systems (including GNU, undocumentedly) support -E instead, but perhaps the safest thing is to use a basic regular expression. Unfortunately on many systems ? and + are not available in basic regexes, but using * instead happens to work in our case.

Thanks to @neverpanic for catching this.

Fixes #210

Apparently Kate requires the <itemDatas> to be inside the <highlighting>
tag whereas QtCreator also accepts it a level higher.

Tested using this DTD:
https://github.com/jgm/highlighting-kate/blob/master/xml/language.dtd

Fix -Werror build without KJ_HAS_BACKTRACE

This avoids an unused function warning for crashHandler.

Fall back to sysconf(_SC_IOV_MAX) if both IOV_MAX and UIO_MAXIOV are undefined

LocalAddress and RemoteAddress were apparently merged into NetworkAddress long ago.