Fix missing annotations

Fix C+1y warnings from Clang.

warning: 'constexpr' non-static member function will not be implicitly
'const' in C++1y; add 'const' to avoid a change in behavior
[-Wconstexpr-not-const]

calculator.capnp style adjusting

p.s. thanks @cstrahan for vim syntax highlighting

Delete snappy code.  It relied on an unsubmitted patch to Snappy's interface and it turns out LZ4 is better anyway so we'll probably integrate with that instead, eventually.

Upgrade gtest to 1.7.0

doc: Fix documentation pseudocode to match description.

Update test script for XCode 5, make sure -stdlib gets in pkg-config configs, use pkg-config in test script, and build RPC tests in test script.

Eliminate the concept of imbuing messages in favor of the simpler concept of setting a cap table directly on MessageReader / getting one from MessageBuilder.  This eliminates capability-context entirely.  This was made possible by the earlier change which moved capabilities to a separate table rather than storing CapDescriptors inline, but I didn't realize it at the time.