Allow Flang kind printing in complex.exp,pointer-to-pointer.exp,vla-ptr-info.exp

Allow Flang kind printing in complex.exp,pointer-to-pointer.exp,vla-ptr-info.exp

In the test cases complex.exp,pointer-to-pointer.exp,vla-ptr-info.exp
fortran.exp routines are not used, which are to determine the type/kind
string. Due to this these test incorrectly fail for Flang.
Now test cases are modified to use fortran.exp routines. fortran.exp
file is modified to add absent routines fortran_complex8 and
fortran_complex16.

gdb/testsuite/ChangeLog

	* lib/fortran.exp (fortran_complex8): New proc.
	(fortran_complex16): New proc.
	* gdb.fortran/complex.exp: Use routines from fortran.exp
	* gdb.fortran/pointer-to-pointer.exp: Likewise.
	* gdb.fortran/vla-ptr-info.exp: Likewise.