Use MACHINE_CPUARCH/TARGET_CPUARCH in preference to MACHINE/TARGET and minor cleanup

[imp]

Summary

MACHINE and TARGET are only applicable to kernel configurations. Since
these are 100% userland options, use the more appropriate
TARGET_CPUARCH/MACHINE_CPUARCH. Adjust TT to be TCA in the
process. Add a comment so I won't have to remove them again in the
future.

Now that we have __TCA, it's more appropriate to use in these cases
than re-writing the filtering code we already have centralized.

Test Plan

make universe

[0mp]

share/mk/src.opts.mk

244

Typo in COMNFIGURATION.

[imp]

fix typo and while I'm at it, adjust comment

[imp]

fixed and regened

[brooks]

LGTM