main: Refactor GetBufferParameteri[64]v.
main: Refactor GetBufferParameteri[64]v.

v2: Split into a refactor commit and an entry point commit.

Reviewed-by: Fredrik Höglund <f487c7598f046a9a67757788cf85ee89028a1b14@kde.org>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler