FortranCInterface: Add support for LLVMFlang mangling

The following `module.f90` file

    module mymodule
    contains
      subroutine mysub()
      end subroutine
    end module

when compiled with `flang-new` (from LLVM 15.0.0) generate the
`_QMmymodulePmysub` symbol.

    $ flang-new -c module.f90
    $ nm module.o
    0000000000000000 T _QMmymodulePmysub

This commit fixes the regular expressions accordingly.
2 files changed