Quick compiler: aarch64 codegen & long_min literal

Int64 overflow during instruction selection caused incorrect
code patterns to emitted in some cases of long operations with
an immediate value of 0x8000000000000000.

The code in question was attempting to determine if the immediate
operand would fit in aarch64 immediate instruction variants.

Internal b/17630605

Change-Id: I8177021b73e51302bc1032387d83b1dd567ed6db