Use the registers g1 and g5 as temporaries for making far jumps and far calls,

Use the registers g1 and g5 as temporaries for making far jumps and far calls,
because saving i1 and i2 to their ``designated'' stack slots corrupts unknown
memory in other functions, standard libraries, and worse.

In addition, this has the benefit of improving JIT performance because we
eliminate writing out 4 instructions in CompilationCallback() and 2 loads and 2
stores.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@7653 91177308-0d34-0410-b5e6-96231b3b80d8