fortran: Testsuite, fix different type naming across compilers.

Gfortran and ifort have different names for data types.  Encapsulate
type names in a library to increase number of supported compilers.
gfortran -4.2 : int4
gfortran>=4.3 : integer(kind=4)
ifort         : INTEGER(4)

2016-04-18  Bernhard Heckel  <bernhard.heckel@intel.com>

gdb/testsuite/Changelog:
	* gdb.fortran/common-block.exp: Use type naming defined in lib fortran.
	* gdb.fortran/derived-type.exp: Use type naming defined in lib fortran.
	* gdb.fortran/multi-dim.exp: Use type naming defined in lib fortran.
	* gdb.fortran/vla-datatypes.exp: Use type naming defined in lib fortran.
	* gdb.fortran/vla-ptype-sub.exp: Use type naming defined in lib fortran.
	* gdb.fortran/vla-ptype.exp: Use type naming defined in lib fortran.
	* gdb.fortran/whatis_type.exp: Use type naming defined in lib fortran.
	* lib/fortran.exp (fortran_int4): New procedure.
	(fortran_real4, fortran_real8, fortran_complex4): Likewise.
	(fortran_logical4): Likewise.