pre-inst-guile

[Thien-Thi Nguyen]

currently check-guile wraps the built guile, setting env vars and such,
so that it can invoke the test-suite/guile-test scheme script.  i would
like to move the wrapping to pre-inst-guile so that we can use it
elsewhere (like for doc/ref/autoconf-macros.texi building) in a
consistent way.  i would examine all Makefile.am to adjust callers.

any objections?

any suggestions on a better name than "./pre-inst-guile"?

thi