Fix unclear wording pointed out by Tim Peters, about the interaction between

^ and the pos argument to re.match().
Also, fixed a typo in libregex.tex.

Doc/lib/libregex.tex

@@ -288,7 +288,7 @@ Compiled regular expression objects support these methods:
   The optional second parameter, \var{pos}, gives an index in the string
   where the search is to start; it defaults to \code{0}.  This is not
   completely equivalent to slicing the string; the \code{'\^'} pattern
-  character matches at the real begin of the string and at positions
+  character matches at the real beginning of the string and at positions
   just after a newline, not necessarily at the index where the search
   is to start.
 \end{funcdesc}