Add half-hearted support for Clang, because its `blocks' are deficient.

[finally] / .gitignore

## Pervasive build machinery.
Makefile.in

## Top-level generated files.
/aclocal.m4
/autom4te.cache/
/configure
/precomp/

## GNU build system machinery installed by `autoreconf'.
/config/compile
/config/config.guess
/config/config.sub
/config/depcomp
/config/install-sh
/config/ltmain.sh
/config/missing
/config/tap-driver.sh
/config/test-driver