8 build/test improvements pushed

[Jim Meyering]

I've just pushed the following.

Mostly just the tedious conversion to make the remaining tests
use gnulib's init.sh framework.  That permitted a little
clean-up of tests/Makefile.am.

  Subject: [PATCH 1/8] build: update build/test tools from gnulib
  Subject: [PATCH 2/8] build: update gnulib submodule to latest
  Subject: [PATCH 3/8] tests: convert to use init.sh
  Subject: [PATCH 4/8] tests: convert bre.sh to use init.sh
  Subject: [PATCH 5/8] tests: convert pcre.sh to use init.sh
  Subject: [PATCH 6/8] tests: remove warning.sh
  Subject: [PATCH 7/8] tests: convert remaining tests to use init.sh
  Subject: [PATCH 8/8] tests: remove .sh suffix from remaining test scripts.