wayland-scanner: guard interface forward declarations by `#ifdef` too
I have some tests that include server and client protocol headers at the same time, this leads to warnings due to identical forward declarations in client and server protocol headers:
In file included from ../subprojects/wlroots/include/wlr/types/wlr_layer_shell_v1.h:16,
from ../src/desktop.h:16,
from ../src/server.h:13,
from ../tests/testlib.c:8:
tests/59830eb@@footest@sta/wlr-layer-shell-unstable-v1-protocol.h:80:34: warning: redundant redeclaration of ‘zwlr_layer_shell_v1_interface’ [-Wredundant-decls]
80 | extern const struct wl_interface zwlr_layer_shell_v1_interface;
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from ../tests/testlib.h:8,
from ../tests/testlib.c:7:
tests/59830eb@@footest@sta/wlr-layer-shell-unstable-v1-client-protocol.h:77:34: note: previous declaration of ‘zwlr_layer_shell_v1_interface’ was here
77 | extern const struct wl_interface zwlr_layer_shell_v1_interface;
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from ../subprojects/wlroots/include/wlr/types/wlr_layer_shell_v1.h:16,
from ../src/desktop.h:16,
from ../src/server.h:13,
from ../tests/testlib.c:8:
tests/59830eb@@footest@sta/wlr-layer-shell-unstable-v1-protocol.h:106:34: warning: redundant redeclaration of ‘zwlr_layer_surface_v1_interface’ [-Wredundant-decls]
106 | extern const struct wl_interface zwlr_layer_surface_v1_interface;
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from ../tests/testlib.h:8,
from ../tests/testlib.c:7:
tests/59830eb@@footest@sta/wlr-layer-shell-unstable-v1-client-protocol.h:103:34: note: previous declaration of ‘zwlr_layer_surface_v1_interface’ was here
103 | extern const struct wl_interface zwlr_layer_surface_v1_interface;
Guarding these #ifndef
s like e.g. enums would avoid that, would that be an option?