Faster grep pattern for identifiers

* lisp/cedet/semantic/symref/grep.el (semantic-symref-perform-search):
Use the `-w` flag instead of wrapping the pattern in regexps that make
matching much slower.  This speeds up `xref-find-references` by about
3× on macOS.

lisp/cedet/semantic/symref/grep.el

@@ -150,15 +150,8 @@ This shell should support pipe redirect syntax."
                            "-l ")
                           ((eq (oref tool searchtype) 'regexp)
                            "-nE ")
-                          (t "-n ")))
-         (greppat (cond ((eq (oref tool searchtype) 'regexp)
-                         (oref tool searchfor))
-                        (t
-                         ;; Can't use the word boundaries: Grep
-                         ;; doesn't always agree with the language
-                         ;; syntax on those.
-                         (format "\\(^\\|\\W\\)%s\\(\\W\\|$\\)"
-                                 (oref tool searchfor)))))
+                          (t "-nw ")))
+         (greppat (oref tool searchfor))
 	 ;; Misc
 	 (b (get-buffer-create "*Semantic SymRef*"))
 	 (ans nil)