Added qt creator's CMakeLists.txt.user to .gitignore.
Set project name in cmake.
Shelled cmake tool modules.
Included cmake tool modules in root CMakeLists.txt.
Moved third-party cmake script to third-party.cmake.
Cleaned up third-party.cmake.
Fixed small header typo.
Added set of known oses to defs.cmake.
Added set of known compilers to defs.cmake.
Told cmake what to do with .tcc files.
CMake now detects host as target if target not specified.
CMake now correctly detects the target compiler.

We also detect if the compiler is gcc-compatible, like clang, so that we can
specify a common subset of build flags.
Shelled compiler-specific cmake modules.
gcc-compat cmake module is now included for gcc-compat compiilers.
cmake: Compiler-specific module now included.
cmake: Our build flags are now exported to cmake.
cmake: Added nav dummy project.
cmake: Added common set of gcc-compatible warnings.
cmake: Added common gcc debug flags.
cmake: Added optional flag for linking guis with ogl on macos.