Platform cleanup
- Define VOGL_METHOD_NAME to be __FUNCSIG__(Windows) or
  __PRETTY_FUNCTION(Linux).
- Kill demangle() code and use VOGL_METHOD_NAME.
- Rewrite vogl_is_debugger_present to not read entire file in and
  allocate vogl memory.
- Kill debugger check for debugger parent: TracerPid should work.
- This routine is called during asserts - which can happen in memory
  subsystem.
Fix voglgen_make_inc to only run when needed, rather than every build.
Merge branch 'master' of https://github.com/ValveSoftware/vogl