Fix sign extension for MIPS64 in makeLibCall function

Fixing sign extension in makeLibCall for MIPS64. In MIPS64 architecture all
32 bit arguments (int, unsigned int, float 32 (soft float)) must be sign
extended. This fixes test "MultiSource/Applications/oggenc/".

Patch by Strahinja Petrovic.

Differential Revision: http://reviews.llvm.org/D7791

llvm-svn: 232943