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/cmd/ksh93/RELEASE93

@@ -1,5 +1,5 @@
 This is a list of changes that have been made since the 12/28/93 version
-of ksh. 
+of ksh.
 
 1.	New features in 12/28/93b
 	a.  If IFS contains two consecutive identical characters belonging
@@ -65,7 +65,7 @@ of ksh.
 	f.  If foo is a function, and not a program, then command foo
 	    now reports that foo isn't found rather than invoking foo.
 	g.  The previous version incorrectly listed -A as an
-	    invocation option.  The -A option is only for set. 
+	    invocation option.  The -A option is only for set.
 	h.  A bug was fixed which caused ksh to loop when execution trace
 	    was enabled and the PS4 prompt required command substitution.
 	i.  A bug which could cause the job control switch character
@@ -179,7 +179,7 @@ of ksh.
 	n.  Variables that were unset but had attributes such as readonly
 	    and export were not listed with readonly, export and typeset.
 	o.  Several problems with signals have been fixed.
-	p.  A bug which prevented ulimit -t from working has been fixed. 
+	p.  A bug which prevented ulimit -t from working has been fixed.
 	    Also, a bug in which failed ulimits could cause a core dump
 	    has also been fixed.
 	q.  A bug in expansion of the form ${name/#pattern/string} and
@@ -225,7 +225,7 @@ of ksh.
 11.	Bugs fixed in 12/28/93e for default OPTIONS
 	a.  Empty command substitutions of the form $() now work.
 	b.  whence -v foo now gives the correct result after calling
-	    builtin -d foo. 
+	    builtin -d foo.
 	c.  A bug in right to left arithmetic assignment for which
 	    the arithmetic expression (( y = x = 1.5 )) did not
 	    yield 1 for y when x was declared typeset -i was fixed.
@@ -247,7 +247,7 @@ of ksh.
 	j.  A bug that caused side effects in subscript evaluation
 	    when tracing was enabled for subscripts using ++ or --
 	    has been fixed.
-	k.  To conform to the Posix standard getopts has been changed
+	k.  To conform to the POSIX standard getopts has been changed
 	    so that the option char is set to ? when it returns with
 	    a non-zero exit status.
 	l.  The handling of \} inside ${name...} has been fixed so
@@ -333,7 +333,7 @@ of ksh.
 	    evaluation has been fixed.
 	d.  A bug when a name reference with a shorter name than
             the variable it references was the subject of a compound
-	    assignment has been fixed. 
+	    assignment has been fixed.
 	e.  A bug which in which assignment to array variables in
 	    a subshell could effect the parent shell has been
 	    fixed.
@@ -348,7 +348,7 @@ of ksh.
 	    fixed.
 	m.  The default base when not specified with typeset -i is
 	    10 in accordance with the documentation.  Previously,
-	    the value was determined by the first assignment.   
+	    the value was determined by the first assignment.
 	n.  A parsing bug in which a # preceded alphanumeric
 	    characters inside a command substitution caused
 	    a syntax error to be reported has been fixed.
@@ -362,7 +362,7 @@ of ksh.
 	a.  I bug in shcomp for compilation of unary operators with [[...]]
 	    has been fixed.
 	b.  A bug in which the value of $? was changed when executing
-	    a keyboard trap has been fixed. 
+	    a keyboard trap has been fixed.
 	c.  The handling of SIGCHLD has been changed so that the
 	    trap is not triggered while executing trap commands
 	    to avoid recursive trap calls.
@@ -449,7 +449,7 @@ of ksh.
 	    or built-in.
 	k.  A callback function can be installed which will give
 	    notification of file duplications and file closes.
-	    
+
 18.	Incompatibilities with 12/28/93 version.
 	None intentional.