This change primarily fixes some -Wconversion warnings from gcc, but
also silences a warning triggered in glslang_tab.cpp, which is generated
code from bison.
There are still several GCC conversion warnings in Types.h due to the
use of bit fields that will be resolved in a future change.
Both debug and release clang builds have segfaulted on recent
changes, non deterministically, while doing the single/multi-thread
test all test files. Removing recent test files, to see if it gives
a clue.
