bogus NLSPATH handling

[jelmd]

ksh93 handles NLSPATH not correctly. E.g. if the catalog name is not set (e.g. see src/lib/libast/tm/tmlocale.c), it stops parsing the path on %C or /LC_MESSAGES (sets last=1), checks for this path and because last is not reset to 0, it takes each consecutive path component as a single locale path to lookup. Since pathpath() gets used for the lookup, this may result in picking up regular executables from ${PATH}.

E.g.:

export NLSPATH=/usr/share/locale/%L/LC_MESSAGES/%N.cat:/usr/share/locale/%l/LC_MESSAGES/%N.cat
ksh93 -c "printf '%T\n' '1 Jan'"

results into Sun ${garbage} 1 13:20:01 MET 2017 whereby garbage are the first 10 bytes of /usr/sbin/share - this is a regular executable. pathpath('share', ...) picks it up, because it is looking up the file in all ${PATH} paths.

Fix is to not blindly stop parsing on %C or /LC_MESSAGES (doesn't make sense to me at all, found no spec, which demands such a behavior) and to be able to supply %T handling a customized catalog to use e.g. ksh93_tm instead of NULL.

NOTE that tcsh per default sets the NLSPATH the same way as shown above.