Initial checkin for sprintmt(3) and vsprintmt(3) documentation.
syslog.3:
Add descriptions of syslogmt(3) and vsyslogmt(3), which are thread-
safe variants with more limited format specifiers.
progname.3:
Added description of the "__progname" variable. This in effect
exposes the cache value used by __prognameGS(). It was necessary
for the proper operation of the thread-safe syslog routines.