The codebase seems to use both “#pragma once“ approach, and “#ifndef / #define” approach,
so I picked pragma once as that one is less typing & less brittle.
When glslang is built with some other build system and lumped/unity builds are used,
without the include guards some headers would get included multiple times, leading to duplicate
declaration errors.
This fixes various issues related to gcc's strict-aliasing warning
by using unions. It also handles various cases hit with
gcc's missing-declarations warning.
- member initializing order in some constructors
- missing default branches in switch-case
- uninitialized variable if switch-case default (uncritical because
program would exit)
- && and || brace warnings in if()
