MinGW: Eliminate dependency on winpthread.

kernel32.dll and msvcrt.dll are the only remaining dependencies.
Merge branch 'master' of github.com:kentonv/capnproto
Fix ekam build.
Treat UTF-8 BOMs as whitespace. Complain if other BOMs or obviously-non-UTF-8 data is seen.
Fixes #72.
Fix todo format.
Fix bug where EzRpcClient would segfault if the target host resolved to multiple addresses and the connection to the first of those failed.
Force headers to be treated as system headers when included by application code.

This prevents the compiler from reporting warnings in these headers while compiling application code. Hopefully this will stem the never-ending stream of complaints from people who enable pedantic warnings.
MSVC: Build and test parts of KJ needed in lite mode.

Thanks to Bryan Boreham <bjboreham@gmail.com> for much help getting this started.
Fix MinGW build.
Fix Windows bug that doesn't happen under wine: stdin defaults to text mode, which of course breaks compiler plugins.
Timeouts: Add convenience helpers to kj::Timer interface for adding a timeout to any Promise.
MSVC: Work around constexpr bugs in generated code.
MSVC: All lite-mode tests pass.

The project file still only compiles a test binary, but it should be easy to separate out a library project from here.

Thanks again to Bryan Boreham <bjboreham@gmail.com> for much help getting this working.
Fix build on non-MSVC compilers.
MSVC: Work around some cases where templates nested in templates trigger compiler bugs.