Add the remaining fp_round libcalls:

FPROUND_F80_F32, FPROUND_PPCF128_F32, 
FPROUND_F80_F64, FPROUND_PPCF128_F64

Support for soften float fp_round operands is added, Mips 
needs this to round f64->f32.

Also added support to soften float FABS result, Mips doesn't 
support double fabs results while in 'single float only' mode.

llvm-svn: 54484