devel/sdl20: unbreak DLOPEN=off after r450461

src/video/x11/SDL_x11vulkan.c:82:28: error: use of undeclared identifier 'VK_KHR_XLIB_SURFACE_EXTENSION_NAME'

else if(SDL_strcmp(VK_KHR_XLIB_SURFACE_EXTENSION_NAME, extensions[i].extensionName) == 0)
                   ^

src/video/x11/SDL_x11vulkan.c:82:64: error: use of undeclared identifier 'extensions'

else if(SDL_strcmp(VK_KHR_XLIB_SURFACE_EXTENSION_NAME, extensions[i].extensionName) == 0)
                                                       ^

src/video/x11/SDL_x11vulkan.c:85:14: error: use of undeclared identifier 'extensions'

SDL_free(extensions);
         ^

src/video/x11/SDL_x11vulkan.c:89:22: error: expected ')'

VK_KHR_SURFACE_EXTENSION_NAME " extension");
^

src/video/x11/SDL_x11vulkan.c:88:21: note: to match this '('

SDL_SetError("Installed Vulkan doesn't implement the "
            ^

src/video/x11/SDL_x11vulkan.c:94:20: error: no member named 'vulkan_xlib_xcb_library' in 'struct SDL_VideoData'

videoData->vulkan_xlib_xcb_library = NULL;
~~~~~~~~~  ^

src/video/x11/SDL_x11vulkan.c:99:22: error: expected ')'

VK_KHR_XCB_SURFACE_EXTENSION_NAME "extension or the "
^

src/video/x11/SDL_x11vulkan.c:98:21: note: to match this '('

SDL_SetError("Installed Vulkan doesn't implement either the "
            ^

src/video/x11/SDL_x11vulkan.c:108:20: error: no member named 'vulkan_xlib_xcb_library' in 'struct SDL_VideoData'

videoData->vulkan_xlib_xcb_library = SDL_LoadObject(libX11XCBLibraryName);
~~~~~~~~~  ^

src/video/x11/SDL_x11vulkan.c:109:24: error: no member named 'vulkan_xlib_xcb_library' in 'struct SDL_VideoData'

if(!videoData->vulkan_xlib_xcb_library)
    ~~~~~~~~~  ^

src/video/x11/SDL_x11vulkan.c:111:20: error: no member named 'vulkan_XGetXCBConnection' in 'struct SDL_VideoData'

videoData->vulkan_XGetXCBConnection =
~~~~~~~~~  ^

src/video/x11/SDL_x11vulkan.c:112:41: error: no member named 'vulkan_xlib_xcb_library' in 'struct SDL_VideoData'

SDL_LoadFunction(videoData->vulkan_xlib_xcb_library, "XGetXCBConnection");
                 ~~~~~~~~~  ^

fatal error: too many errors emitted, stopping now [-ferror-limit=]

PR: 232931