Use paired immediates for large constants.

Use paired immediates for large constants.

The double-to-int and double-to-long instructions were loading constants
from .word directives, which wastes space in the CPU data cache.  This
replaces a single LDR with a pair of data operations.

We don't actually use the double-to-long handler (the ARM EABI lib
does the right thing), and double-to-int is handled by VFP on newer
devices, but on older devices this may help a smidgeon.  Mostly it just
looks nicer when you don't have .words lying around.

Also picks up a change that should be in the armv7-a generated file but
got lost in all of today's various mergings (float compare tweak).