Rename version.h to libweston/version.h

This is an installed public header, and without the subdir would surely
conflict with something else.

include/libweston/meson.build is necessary for putting the generated header in
the right subdirectory so that '#include <libweston/version.h>' can work.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>

compositor/main.c

@@ -52,7 +52,7 @@
 #include "../shared/helpers.h"
 #include "../shared/string-helpers.h"
 #include "git-version.h"
-#include "version.h"
+#include <libweston/version.h>
 #include "weston.h"
 
 #include <libweston/backend-drm.h>