Port exclude.c and exclude.h to more non-GNU systems, e.g. Solaris 7.
(EXCLUDE_ANCHORED, EXCLUDE_INCLUDE, EXCLUDE_WILDCARDS):
Choose values that are less likely to collide with system fnmatch
options.
(free_exclude): New decl.
(add_exclude, add_exclude_file): Now takes int options arg.
(excluded_filename): No longer requires options arg, as the options
are determined by add_exclude. Now returns bool, not int.
