Fix a large number of typos and other problems (#110)

Most of these fixes are for typos and extra whitespace at the
end of lines. These are the notable changes:
- Fixed a compatibility issue with how asterisks are displayed
  using certain fonts. Bug report: https://github.com/att/ast/issues/764
- Fixed a bug in the man page that caused searches for the '|'
  character to fail. Bug report: https://github.com/att/ast/issues/871
- Removed a duplicate description of 'set -B' from the man
  page. Bug report: https://github.com/att/ast/issues/789
- Added documentation for options missing from the ksh man
  page (applies to 'hist -N', 'sleep -s', 'whence -q' and
  many of ulimit's options). Bug reports:
  https://github.com/att/ast/issues/948
  https://github.com/att/ast/issues/503#issuecomment-386649715
  https://github.com/att/ast/issues/507#issuecomment-507924608
- Applied the following ksh2020 documentation fixes:
  https://github.com/att/ast/pull/351
  https://github.com/att/ast/pull/352
- Fixed a minor GCC -Wformat warning in procopen.c by changing
  a sentinel to NULL.

src/lib/libast/misc/fastfind.c

@@ -24,7 +24,7 @@
  *	FF_dir	FF_gnu with sfgetl/sfputl and trailing / on dirs (FF_dir_magic)
  *	FF_typ	FF_dir with (mime) types (FF_typ_magic)
  *
- * the bigram encoding steals the eighth bit (that's why its FF_old)
+ * the bigram encoding steals the eighth bit (that's why it's FF_old)
  * maybe one day we'll limit it to readonly:
  *
  * 0-2*FF_OFF	 likeliest differential counts + offset to make nonnegative 

src/lib/libast/misc/procopen.c

@@ -599,7 +599,7 @@ procopen(const char* cmd, char** argv, char** envv, long* modv, int flags)
 			if (!fork())
 			{
 				sfsprintf(path, sizeof(path), "%d", getppid());
-				execlp("trace", "trace", "-p", path, NiL);
+				execlp("trace", "trace", "-p", path, NULL);
 				_exit(EXIT_NOTFOUND);
 			}
 			sleep(2);