libobs-opengl: Load EGL via Glad on Wayland platform

We need to have EGL extensions loaded when dealing with DMA-BUFs.

EGL_EXT_image_dma_buf_import: This extension is required to import
DMA-BUFs with the modifier-less path. It is limited to buffers with 3
planes. [1]

EGL_EXT_image_dma_buf_import_modifiers: This extension is required to
import DMA-BUFs with an explicit modifier. It raises the limit of buffer
planes to 4, which is the maximum planecount for DMA-BUFs. [2]

[1] https://www.khronos.org/registry/EGL/extensions/EXT/EGL_EXT_image_dma_buf_import.txt
[2] https://www.khronos.org/registry/EGL/extensions/EXT/EGL_EXT_image_dma_buf_import_modifiers.txt

libobs-opengl/gl-wayland-egl.c

@@ -209,8 +209,14 @@ static struct gl_platform *gl_wayland_egl_platform_create(gs_device_t *device,
 		goto fail_load_gl;
 	}
 
+	if (!gladLoadEGL()) {
+		blog(LOG_ERROR, "Unable to load EGL entry functions.");
+		goto fail_load_egl;
+	}
+
 	goto success;
 
+fail_load_egl:
 fail_load_gl:
 	egl_context_destroy(plat);
 fail_context_create: