Move weston-egl-ext.h to shared

Given that it's used by clients, it's really the very definition of
shared.

Signed-off-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Derek Foreman <derekf@osg.samsung.com>
diff --git a/Makefile.am b/Makefile.am
index 7743158..8627e5e 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -111,7 +111,7 @@
 	shared/timespec-util.h				\
 	shared/zalloc.h					\
 	shared/platform.h				\
-	libweston/weston-egl-ext.h
+	shared/weston-egl-ext.h
 
 lib_LTLIBRARIES += libweston-desktop-@LIBWESTON_MAJOR@.la
 libweston_desktop_@LIBWESTON_MAJOR@_la_CPPFLAGS = $(AM_CPPFLAGS) -DIN_WESTON
diff --git a/libweston/weston-egl-ext.h b/shared/weston-egl-ext.h
similarity index 100%
rename from libweston/weston-egl-ext.h
rename to shared/weston-egl-ext.h