* lib/regextype.c (get_regex_type_synonym): don't return regex
dialect Y as a synonym of dialect X, if we're not in fact going to
include X. Accept a CONTEXT parameter in order to identify this
situation. This ensures that the bug fixed in commit
e2c673cbcdc325a3a2e9dd02169bb4a42c61bc48 stays fixed for any
permutation of regex_map.
* lib/regextype.h: update prototype of get_regex_type_synonym.
* lib/regexprops.c (describe_all): Pass the new context parameter.
* doc/regexprops.texi: regenerate this file.