Regexp-quote strings of avy-goto-char* functions.

Before this commit, avy-goto-char with char ^ would inf-loop because the
resulting string "^" is treated as a regular expressions.  However, with
the avy-goto-char* function, the char should be treated literally.  For
example, in Clojure ^:foo is treated as metadata annotation and thus ^
is a likely jump target.

avy-jump.el

@@ -236,17 +236,17 @@ The window scope is determined by `avy-all-windows'.
 When ARG is non-nil, flip the window scope."
   (interactive "P")
   (avy--generic-jump
-   (string (read-char "char: ")) arg))
+   (regexp-quote (string (read-char "char: "))) arg))
 
 ;;;###autoload
 (defun avy-goto-char-2 (&optional arg)
   "Read two chars and jump to them in current window.
 When ARG is non-nil, flip the window scope."
   (interactive "P")
   (avy--generic-jump
-   (string
-    (read-char "char 1: ")
-    (read-char "char 2: "))
+   (regexp-quote (string
+		  (read-char "char 1: ")
+		  (read-char "char 2: ")))
    arg))
 
 ;;;###autoload