all: rename nm-glib-compat.h to nm-glib.h, use everywhere

Rather than randomly including one or more of <glib.h>,
<glib-object.h>, and <gio/gio.h> everywhere (and forgetting to include
"nm-glib-compat.h" most of the time), rename nm-glib-compat.h to
nm-glib.h, include <gio/gio.h> from there, and then change all .c
files in NM to include "nm-glib.h" rather than including the glib
headers directly.

(Public headers files still have to include the real glib headers,
since nm-glib.h isn't installed...)

Also, remove glib includes from header files that are already
including a base object header file (which must itself already include
the glib headers).

src/main-utils.h

@@ -21,7 +21,7 @@
 #ifndef __MAIN_UTILS_H__
 #define __MAIN_UTILS_H__
 
-#include <glib.h>
+#include "nm-glib.h"
 
 void     nm_main_utils_ensure_root (void);