Add #ifdef HB_USE_ATEXIT to fix -Wunused-function warnings

src/hb-common.cc

diff --git a/src/hb-common.cc b/src/hb-common.cc
index d308f36..8837cef 100644
--- a/src/hb-common.cc
+++ b/src/hb-common.cc
@@ -235,7 +235,7 @@
 static hb_language_item_t *langs;
 
 #ifdef HB_USE_ATEXIT
-static inline
+static
 void free_langs (void)
 {
   while (langs) {

src/hb-ft.cc

diff --git a/src/hb-ft.cc b/src/hb-ft.cc
index 883f26f..7e75ba9 100644
--- a/src/hb-ft.cc
+++ b/src/hb-ft.cc
@@ -467,11 +467,13 @@
 
 static FT_Library ft_library;
 
-static inline
+#ifdef HB_USE_ATEXIT
+static
 void free_ft_library (void)
 {
   FT_Done_FreeType (ft_library);
 }
+#endif
 
 static FT_Library
 get_ft_library (void)

src/hb-shape.cc

diff --git a/src/hb-shape.cc b/src/hb-shape.cc
index 74747f8..100fb3c 100644
--- a/src/hb-shape.cc
+++ b/src/hb-shape.cc
@@ -279,11 +279,13 @@
 
 static const char **static_shaper_list;
 
-static inline
+#ifdef HB_USE_ATEXIT
+static
 void free_static_shaper_list (void)
 {
   free (static_shaper_list);
 }
+#endif
 
 /**
  * hb_shape_list_shapers:

src/hb-shaper.cc

diff --git a/src/hb-shaper.cc b/src/hb-shaper.cc
index 6ae2601..580b95c 100644
--- a/src/hb-shaper.cc
+++ b/src/hb-shaper.cc
@@ -40,12 +40,14 @@
 
 static const hb_shaper_pair_t *static_shapers;
 
-static inline
+#ifdef HB_USE_ATEXIT
+static
 void free_static_shapers (void)
 {
   if (unlikely (static_shapers != all_shapers))
     free ((void *) static_shapers);
 }
+#endif
 
 const hb_shaper_pair_t *
 _hb_shapers_get (void)