Implement logic for -fgnuc-version= argument required by LLVM.
Implement logic for -fgnuc-version= argument required by LLVM.

Signed-off-by: Joao Matos <c510cd8607f92e1e09fd0b0d0d035c16d2428fa4@tritao.eu>

zillemarco/CppSharp,ddobrev/CppSharp,zillemarco/CppSharp,zillemarco/CppSharp,mono/CppSharp,ddobrev/CppSharp,mono/CppSharp,zillemarco/CppSharp,zillemarco/CppSharp,mono/CppSharp,mono/CppSharp,mono/CppSharp,ddobrev/CppSharp,mono/CppSharp,ddobrev/CppSharp,ddobrev/CppSharp