gdb/fortran: Add allocatable type qualifier

Types in Fortran can have the 'allocatable' qualifier attached to
indicate that memory needs to be explicitly allocated by the user.
This patch extends GDB to show this qualifier when printing types.

Lots of tests results are then updated to include this new qualifier
in the expected results.

gdb/ChangeLog:

	* f-typeprint.c (f_type_print_base): Print 'allocatable' type
	qualifier.
	* gdbtypes.h (TYPE_IS_ALLOCATABLE): Define.

gdb/testsuite/ChangeLog:

	* gdb.fortran/vla-datatypes.exp: Update expected results.
	* gdb.fortran/vla-ptype.exp: Likewise.
	* gdb.fortran/vla-type.exp: Likewise.
	* gdb.fortran/vla-value.exp: Likewise.