DATASET-951: Allow ABI env var to set -m32/-m64

Conflicts:
	lang/gcc47/distinfo
Rename isaexec -> abiexec and make default ABI=32.
Merge branch 'joyent/feature/multiarch/2014Q3' into joyent/release/2014Q3

Conflicts:
	lang/gcc47/distinfo
Update 'joyent' submodule.