Avoid some regex uses.

Avoid some regex uses.

* lib/autoconf/general.m4 (_AC_DEFINE_Q): Use m4_format rather
than m4_bpatsubst to grab string prefix.
* lib/autoconf/status.m4 (_AC_CONFIG_REGISTER)
(_AC_CONFIG_REGISTER_DEST, AC_CONFIG_SUBDIRS): Likewise.
(_AC_FILE_DEPENDENCY_TRACE_COLON): Use m4_translit instead of
m4_bpatsubst to change bytes.
(_AC_CONFIG_DEPENDENCY_DEFAULT): Use m4_index rather than
m4_bmatch to find byte.
(_AC_CONFIG_COMPUTE_DEST): New helper macro.

Signed-off-by: Eric Blake <ebb9@byu.net>