Escape single quotes in docstrings

Fixes warnings:

    purescript-font-lock.el:448:2: Error: docstring has wrong usage of unescaped single quotes (use \=' or different quoting such as `...')
    purescript-indent.el:1321:2: Error: docstring has wrong usage of unescaped single quotes (use \=' or different quoting such as `...')
    purescript-mode.el:88:2: Error: docstring has wrong usage of unescaped single quotes (use \=' or different quoting such as `...')

Author: Hi-Angel

purescript-font-lock.el

@@ -448,7 +448,7 @@ that should be commented under LaTeX-style literate scripts."
 (defun turn-on-purescript-font-lock ()
   "Turns on font locking in current buffer for PureScript 1.4 scripts.
 
-Changes the current buffer's `font-lock-defaults', and adds the
+Changes the current buffer\\='s `font-lock-defaults', and adds the
 following variables:
 
    `purescript-keyword-face'      for reserved keywords and syntax,
@@ -470,7 +470,7 @@ Use the variable `font-lock-maximum-decoration' to choose
 non-default levels of fontification.  For example, adding this to
 .emacs:
 
-  (setq font-lock-maximum-decoration '((purescript-mode . 2) (t . 0)))
+  (setq font-lock-maximum-decoration \\='((purescript-mode . 2) (t . 0)))
 
 uses level two fontification for `purescript-mode' and default level for
 all other modes.  See documentation on this variable for further
@@ -480,17 +480,17 @@ To alter an attribute of a face, add a hook.  For example, to change
 the foreground colour of comments to brown, add the following line to
 .emacs:
 
-  (add-hook 'purescript-font-lock-hook
+  (add-hook \\='purescript-font-lock-hook
       (lambda ()
-          (set-face-foreground 'purescript-comment-face \"brown\")))
+          (set-face-foreground \\='purescript-comment-face \"brown\")))
 
 Note that the colours available vary from system to system.  To see
 what colours are available on your system, call
 `list-colors-display' from emacs.
 
 To turn font locking on for all PureScript buffers, add this to .emacs:
 
-  (add-hook 'purescript-mode-hook 'turn-on-purescript-font-lock)
+  (add-hook \\='purescript-mode-hook \\='turn-on-purescript-font-lock)
 
 To turn font locking on for the current buffer, call
 `turn-on-purescript-font-lock'.  To turn font locking off in the current

purescript-indent.el

@@ -1321,7 +1321,7 @@ of the regions to move."
 (defun purescript-indent-align-def (p-arg type)
   "Align guards or rpurs within the current definition before point.
 If P-ARG is t align all defs up to the mark.
-TYPE is either 'guard or 'rpurs."
+TYPE is either \\='guard or \\='rpurs."
   (save-excursion
     (let (start-block end-block
                       (maxcol (if (eq type 'rpurs) purescript-indent-rpurs-align-column 0))

purescript-mode.el

@@ -87,7 +87,7 @@ When MESSAGE is non-nil, display a message with the version."
 ;;;###autoload
 (defun purescript-customize ()
   "Browse the purescript customize sub-tree.
-This calls 'customize-browse' with purescript as argument and makes
+This calls `customize-browse' with purescript as argument and makes
 sure all purescript customize definitions have been loaded."
   (interactive)
   ;; make sure all modules with (defcustom ...)s are loaded