tests/test-strict

util._matcher: speed up regexp matching.

In 4babaa52badf, Benoit made a change that substantially slows matching
when a big .hgignore file is in play, because it calls into the regexp
matching engine potentially hundreds of times per file to be matched.

I've partly rolled back his change, so that we only call into the matcher
once per file, but preserved the ability to report a meaningful error
message if there's a syntax error in the regexp.

#!/bin/sh

hg init

echo a > a
hg ci -d '0 0' -Ama

hg an a

echo "[ui]" >> $HGRCPATH
echo "strict=True" >> $HGRCPATH

hg an a
hg annotate a

echo % should succeed - up is an alias, not an abbreviation

hg up