Add support for converting VLDR <reg>,=<constant> to a VMOV instruction when appropriate.

Add support for converting VLDR <reg>,=<constant> to a VMOV instruction when appropriate.

	PR gas/18500
gas	* config/tc-arm.c (is_double_a_single): New function.
	(double_to_single): New function.
	(move_or_literal_pool): Add support for	converting VLDR to VMOV.

tests	* gas/arm/vfpv2-ldr_immediate.s: New test case.
	* gas/arm/vfpv2-ldr_immediate.d: Expected disassembly.
	* gas/arm/vfpv3-ldr_immediate.s: New test case.
	* gas/arm/vfpv3-ldr_immediate.d: Expected disassembly.
	* gas/arm/vfpv3xd-ldr_immediate.s: New test case.
	* gas/arm/vfpv3xd-ldr_immediate.d: Expected disassembly.