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.

docs/ksh/builtins.html

@@ -472,7 +472,7 @@ be freed before returning from you built-in, because by default,
 <TT>ksh</TT> will terminate you built-in in the event of an
 interrupt and the memory will not be freed.
 <P>
-The best way to to allocate variable sized storage is
+The best way to allocate variable sized storage is
 through calls to the <STRONG>stak</STRONG> library
 which is included in <STRONG>libast</STRONG>
 and which is used extensively by <TT>ksh</TT> itself.