kwset: improve performance by inlining more

Problem reported by Norihiro Tanaka in <http://bugs.gnu.org/17229#55>.
* src/kwset.c (bmexec_trans): Rename from bmexec, and make it inline.
(bmexec): New implementation, which calls bmexec_trans.  This helps
GCC inline more aggressively with the default optimization, and
improves performance 25% with the reported benchmark on my host.
gnulib: update to latest

* gnulib: This fixes a bug whereby running bootstrap
would remove our build-aux/git-log-fix file.