automake: refactoring: factor out common cpp-like flags * automake.in (@cpplike_flags): In this new variable... (C, C++, Objective C, Objective C++, Unified Parallel C, Preprocessed Assembler, Preprocessed Fortran, Preprocessed Fortran 77): ... to be used by registration (with the 'register_language' subroutine) of these languages. This is a refactoring meant to simplify future changes; no semantic change is intended. Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>