Remove -disable-mips-abicall and -enable-mips-absolute-call command-line

options, which don't appear to be useful.  -enable-mips-absolute-call is
completely unused (and unless I'm mistaken, is supposed to have the 
same effect that -relocation-model=dynamic-no-pic should have), 
and -disable-mips-abicall appears to be effectively a 
synonym for -relocation-model=static. Adjust the few users of hasABICall
to checks which seem more appropriate.  Update MipsSubtarget, 
MipsTargetMachine, and MipselTargetMachine to synchronize with recent 
changes.

llvm-svn: 77938