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.

src/cmd/ksh93/sh/path.c

@@ -1198,7 +1198,7 @@ pid_t path_spawn(Shell_t *shp,const char *opath,register char **argv, char **env
 	if(*path!='/' && path!=opath)
 	{
 		/*
-		 * The following code because execv(foo,) and execv(./foo,)
+		 * The following code is because execv(foo,) and execv(./foo,)
 		 * may not yield the same results
 		 */
 		char *sp = (char*)sh_malloc(strlen(path)+3);