gdb/fortran: Support for single/double type modifiers

gdb/fortran: Support for single/double type modifiers

Extend the Fortran parser to support 'single precision' and 'double
precision' types as well 'single complex' and 'double complex' types.

gdb/ChangeLog:

	* f-exp.y (COMPLEX_KEYWORD, SINGLE, DOUBLE, PRECISION): New
	tokens.
	(typebase): New patterns for complex, single/double precision, and
	single/double complex.
	(f77_keywords): Change token for complex keyword, and add single,
	double, and precision keywords.

gdb/testsuite/ChangeLog:

	* gdb.fortran/type-kinds.exp (test_cast_1_to_type_kind): Handle
	casting to type with no kind specified.
	(test_basic_parsing_of_type_kinds): Additional tests for types
	with no kind specified, and add tests for single/double
	precision/complex types.

Change-Id: I9c82f4d392c58607747bd08862c1ee330723a1ba