Lots of man page fixes and some other minor fixes (#284)

Noteworthy changes:
- The man pages have been updated to fix a ton of instances of
  runaway underlining (this was done with `sed -i 's/\\f5/\\f3/g'`
  commands). This commit dramatically increased in size because
  of this change.
- The documentation for spawnveg(3) has been extended with
  information about its usage of posix_spawn(3) and vfork(2).
- The documentation for tmfmt(3) has been updated with the changes
  previously made to the man pages for the printf and date builtins
  (though the latter builtin is disabled by default).
- The shell's tracked alias tree (hash table) is now documented in
  the shell(3) man page.
- Removed the commented out regression test for an ERRNO variable
  as the COMPATIBILITY file states it was removed in ksh93.

docs/ksh/features.html

@@ -21,7 +21,7 @@ dd	{ margin-left:3em; }
 <P><CENTER><FONT color=red><FONT face=courier><H3><A name="ksh features">ksh features</A></H3></FONT></FONT></CENTER>
 KSH-93 is the most recent version of the KornShell Language described in
 <EM>The KornShell Command and Programming Language</EM>,
-by Morris Bolsky and David Korn of AT&amp;T Research (nee Bell Laboratories).
+by Morris Bolsky and David Korn of AT&amp;T Research.
 The KornShell is a shell programming language,
 which is upward compatible with
 <EM>sh</EM>