Don't call isIntegerConstantExpr if isValueDependent

...some paths trough clang::Expr::isIntegerConstantExpr (esp. if
non-CPlusPlus11) assert the assumption that the given expr is not
value-dependent, so it appears to be a prereq

Change-Id: Ibc5fe472ea3f91b31c8cb7f06c4b7c7f4d6831a3
No need for CppunitTest_odk_checkapi to disable compiler plugins

Change-Id: I258a3bb0fafbea5fa41133c0f223162cc416b36b
Remove unused gb_*_disable_compiler_plugins

Change-Id: Ia6395282916011d75a4fa01aa12e96d866621411