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

Implement mutex and once-init synchronization primitives.  Wrap pthreads for now, but plan on raw futexes later.

Enable some useful Clang warnings, fix some bugs it detected.  Especially, eliminate all dynamic initializers.

Mark every destructor "noexcept(false)" unless it is very clearly noexcept.  The change in C++11 making destructors default-noexcept was a mistake.

Basic code generation starting to work.  My machine just did something weird so I'm submitting and pushing in case of imminant hardware failure...

Moar type-safety, rewriting WireFormat to avoid descriptors (incomplete), decided struct pointers should point at the beginning of the struct after all.