arm: Declare MVE types internally via pragma

Move the implementation of MVE ACLE types from arm_mve_types.h to
inside GCC via a new pragma, which replaces the prior type
definitions.  This allows for the types to be used internally for
intrinsic function definitions.

gcc/ChangeLog:

	* config.gcc (arm*-*-*): Add arm-mve-builtins.o to extra_objs.
	* config/arm/arm-c.c (arm_pragma_arm): Handle "#pragma GCC arm".
	(arm_register_target_pragmas): Register it.
	* config/arm/arm-protos.h: (arm_mve::arm_handle_mve_types_h): New
	prototype.
	* config/arm/arm_mve_types.h: Replace MVE type definitions with
	new pragma.
	* config/arm/t-arm: (arm-mve-builtins.o): New target rule.
	* config/arm/arm-mve-builtins.cc: New file.
	* config/arm/arm-mve-builtins.def: New file.
	* config/arm/arm-mve-builtins.h: New file.

gcc/testsuite/ChangeLog:

	* gcc.target/arm/mve/mve.exp: Add new subdirectories.
	* gcc.target/arm/mve/general-c/type_redef_1.c: New test.
	* gcc.target/arm/mve/general/double_pragmas_1.c: New test.
	* gcc.target/arm/mve/general/nomve_1.c: New test.