[Patch libgcc] Enable HCmode multiply and divide (mulhc3/divhc3)

[Patch libgcc] Enable HCmode multiply and divide (mulhc3/divhc3)

This patch arranges for half-precision complex multiply and divide
routines to be built if __LIBGCC_HAS_HF_MODE__.  This will be true
if the target supports the _Float16 type.

libgcc/

	PR target/63250
	*  Makefile.in (lib2funcs): Build _mulhc3 and _divhc3.
	* libgcc2.h (LIBGCC_HAS_HF_MODE): Conditionally define.
	(HFtype): Likewise.
	(HCtype): Likewise.
	(__divhc3): Likewise.
	(__mulhc3): Likewise.
	* libgcc2.c: Support _mulhc3 and _divhc3.

From-SVN: r240043