1. Add all characters from ~ expansion as protected to be not interpreted

as pattern meta chars.

2. GLOB_ERR and gl_errfunc are supposed to work only for real directories

per POSIX, so don't act on missing or plain files, for ENOENT or ENOTDIR
(as TODO in the code suggested).

3. Remove the hack in the manpage describing how to skip ENOENT and ENOTDIR

in gl_errfunc, it is unneeded now.

4. Set errno to ENAMETOOLONG if g_Ctoc() expansion fails in g_opendir(),

as in other places in the code which are wrappers around system functions.