even if the specified file is not in the PATH.
This change enforces security and makes it conform to POSIX.
Closes PR #6794.
I thought Christos committed this but not appeared yet. :)
The setstackmark()/popstackmark() pair in dotcmd(), used for freeing
stack storage possibly allocated by find_dot_file(), is redundant for now
since dotcmd() is surrounded by another pair in evalcommand().
This redundancy, however, may help future modifications
(suggested by Christos).
362c3e31c9