recheck when needed. Before it used to be the case that we could only
use the cached entry once. Once the cached entry was used, we removed
it from the cache. Now it is kept forever.
- new dir.c function: Dir_FindHereOrAbove:
Search for a path in the current directory and then all the directories
above it in turn until the path is found or we reach the root ("/").
- add hooks to use it in main.c for -m and syspath (compiled in
_PATH_DEFSYSPATH and $MAKESYSPATH).
- updated man page
search list that will be used. Thus 'dot' and 'cur' will appear in
${.PATH} either at the start or end depending on .DOTLAST even though
they are not strictly in dirSearchPath.
When .CURDIR is assigned to - re-set the 'cur' Path.
Finally, when checking subdirs, look in 'dot' and 'cur' (first or last
depending on .DOTLAST) just as we do in other situations.
