cmd/cc: delete lexbody, macbody

These files were left behind for the C implementation of the assemblers.
They're no longer needed.

This is the last of the cmd/cc directory.

Change-Id: I9231b23c27fead5695000097aeb694824747677d
Reviewed-on: https://go-review.googlesource.com/6367Reviewed-by: Minux Ma <minux@golang.org>