s3:lib: add samba_path_matching_regex_sub1_create()

s3:lib: add samba_path_matching_regex_sub1_create()

This will allow the usage 'POSIX Basic Regular Expression'
instead of 'ms wildcard' strings.

We allow exactly one 'subexpression' starting with '\(' and
ending with '\)' in order to find a replacement (byte) region
in the matching string.

This will be used in the vfs_preopen module in the following
commits.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>