Use 'dumb quotes' rather than `really dumb quotes'

Back in the far-off twentieth century, it was normal on unix
workstations for U+0060 GRAVE ACCENT to be drawn as "‛" and for U+0027
APOSTROPHE to be drawn as "’". This led to the convention of using
them as poor-man's ‛smart quotes’ in ASCII-only text.

However, "'" is now universally drawn as a vertical line, and "`" at a
45-degree angle, making them an `odd couple' when used together.

Unfortunately, there are lots of very old strings in glib, and also
lots of new strings in which people have kept up the old tradition,
perhaps entirely unaware that it used to not look stupid.

Fix this by just using 'dumb quotes' everywhere.

https://bugzilla.gnome.org/show_bug.cgi?id=700746

gio/kqueue/dep-list.c

@@ -75,7 +75,7 @@ dep_list* dl_create (char *path, ino_t inode)
  * Create a shallow copy of a list.
  *
  * A shallow copy is a copy of a structure, but not the copy of the
- * contents. All data pointers (`path' in our case) of a list and its
+ * contents. All data pointers ('path' in our case) of a list and its
  * shallow copy will point to the same memory.
  *
  * @param[in] dl A pointer to list to make a copy. May be NULL.
@@ -222,9 +222,9 @@ error:
  * will be removed from the both lists. Items are comapred by a filename.
  * 
  * @param[in,out] before A pointer to a pointer to a list. Will contain items
- *     which were not found in the `after' list.
+ *     which were not found in the 'after' list.
  * @param[in,out] after  A pointer to a pointer to a list. Will containt items
- *     which were not found in the `before' list.
+ *     which were not found in the 'before' list.
  **/
 void
 dl_diff (dep_list **before, dep_list **after)

gio/kqueue/kqueue-thread.c

@@ -215,7 +215,7 @@ _kqueue_thread_func (void *arg)
 
   for (;;)
     {
-      /* TODO: Provide more items in the `eventlist' to kqueue(2).
+      /* TODO: Provide more items in the 'eventlist' to kqueue(2).
        * Currently the backend takes notifications from the kernel one
        * by one, i.e. there will be a lot of system calls and context
        * switches when the application will monitor a lot of files with