before including windows.h.

Visual Studio 2017 (14.11.25503, 19.11.25508.2) needs `#include <wincrypt.h>` for CryptGenRandom etc.

People see files named "md5" and get worried about security issues, even though we're using it only as a *non-cryptographic* PRNG. So, I renamed the files to type-id.*, encapsulated the code better to make clear that it's only used to generate type IDs, and added comments clarifying that we're not expecting it to be collision-proof.

Fixes #482.

Fixes #251

Example:

    const data :Data = embed "some-file.dat";

Files are looked up the same way an import would be.

You can use embed when Data or Text is expected. You can also use it when a struct type is expected -- the file will be interpreted as a message using standard binary serialization.

See changes to test.capnp for example.

Currently only supported through generated code, not in the dynamic API. Not exactly sure how to expose this in the dynamic API...

For portions currently copyright by Kenton (most of it), transfer copyright to Sandstorm Development Group, Inc. (Kenton's company).

The license change is practically meaningless, as MIT and BSD 2-clause are legally equivalent. However, the BSD 2-clause license is sometimes confused for its ugly siblings, BSD 3-clause and BSD 4-clause. The MIT license is more immediately recognizeable for what it is.

Rémy Blank and Jason Choy (the two non-trivial contributors) are on record as approving this change:

https://groups.google.com/d/msg/capnproto/xXDd2HUOCcc/gbe_COIuXKYJ

Define new KJ constants for min/max integer values and inf/nan, then remove all use of numeric_limits.

Interface code generation.  Also update method grammar to allow multiple returns, and allow specifying request/response structs instead of parameter lists.

Extend interface grammar to support inheritance, and update compiler to properly compile interfaces.

Require a colon before 'group' or 'union' except for unnamed unions as well as the legacy case of a named union with an ordinal (where the colon is optional).

New method isFoo() exists for union fields only and returns true if foo is the active union field.

Unnamed unions WIP.  About to change MemberInfo format, which will require re-bootstrapping the code generator.

Arrange for compiler to send to the code generator the complete contents of all files listed on the command line, all first-level dependencies of those files, and parent scopes of those dependencies, but nothing more.  This means it's sometimes possible to compile a schema file without parsing all transitive dependencies.  Also, in 'decode' mode, don't compile annotations, so that the files defining those annotations need not be opened at all.

Compiler actually running plugins!  Hooked it up to capnpc-capnp (the loopback plugin).  Working on getting the output identical to the old capnpc...  still a few bugs left.

Add utility code for really nice command-line option parsing and start using it in the compiler (still WIP).