Move lexinit, typeinit, lexinit1, and lexfini into new universe.go
file, and give them a more idiomatic and descriptive API. No code
changes.

Change-Id: I0e9b25dcc86ad10f4b990dc02bd33477b488cc85
Reviewed-on: https://go-review.googlesource.com/20604Reviewed-by: Robert Griesemer <gri@golang.org>