This code implements most of mips16 hardfloat as it is done by gcc.

In this case, essentially it is soft float with different library routines.
The next step will be to make this fully interoperational with mips32 floating
point and that requires creating stubs for functions with signatures that
contain floating point types.

I have a more sophisticated design for mips16 hardfloat which I hope to
implement at a later time that directly does floating point without the need
for function calls.

The mips16 encoding has no floating point instructions so one needs to
switch to mips32 mode to execute floating point instructions.

llvm-svn: 170259