Implement fma and mad
Simplify Float16.{fma,mad}
Merge branch 'fma'

Conflicts:
	base/float16.jl
Use fma instrinsic instead of fma function
Merge branch 'fma'
Rename mad to muladd
Add documentation for fma and muladd
Document cld
Merge branch 'cld'
Merge branch 'fma'