gdb/fortran: Handle internal function calls

gdb/fortran: Handle internal function calls

If an convenience function is defined in python (or guile), then
currently this will not work in Fortran, instead the user is given
this message:

  (gdb) set language fortran
  (gdb) p $myfunc (3)
  Cannot perform substring on this type

Compare this to C:

  (gdb) set language c
  (gdb) p $myfunc (3)
  $1 = 1

After this patch we see the same behaviour in both C and Fortran.
I've extended the test to check that all languages can call the
convenience functions - only Fortran was broken.

When calling convenience functions in Fortran we don't need to perform
the same value preparation (passing by pointer) that we would for
calling a native function - passing the real value is fine.

gdb/ChangeLog:

	* eval.c (evaluate_subexp_standard): Handle internal functions
	during Fortran function call handling.

gdb/testsuite/ChangeLog:

	* gdb.python/py-function.exp: Check calling helper function from
	all languages.
	* lib/gdb.exp (gdb_supported_languages): New proc.