Use EGL to retrieve pointers if available

EGL is available on different platforms, so we should favor it, if
available. This also allows us to decouple EGL from GLX, and use the
former without the latter being compiled in.

src/dispatch_common.c

@@ -642,28 +642,32 @@ epoxy_get_bootstrap_proc_address(const char *name)
 void *
 epoxy_get_proc_address(const char *name)
 {
-#ifdef _WIN32
+#if PLATFORM_HAS_EGL
+    GLenum egl_api = EGL_NONE;
+
+    if (!epoxy_current_context_is_glx())
+      egl_api = epoxy_egl_get_current_gl_context_api();
+
+    switch (egl_api) {
+    case EGL_OPENGL_API:
+    case EGL_OPENGL_ES_API:
+        return eglGetProcAddress(name);
+    case EGL_NONE:
+        break;
+    }
+#endif
+
+#if defined(_WIN32)
     return wglGetProcAddress(name);
 #elif defined(__APPLE__)
     return epoxy_gl_dlsym(name);
-#else
-    if (epoxy_current_context_is_glx()) {
+#elif PLATFORM_HAS_GLX
+    if (epoxy_current_context_is_glx())
         return glXGetProcAddressARB((const GLubyte *)name);
-    } else {
-#if PLATFORM_HAS_EGL
-        GLenum egl_api = epoxy_egl_get_current_gl_context_api();
-
-        switch (egl_api) {
-        case EGL_OPENGL_API:
-        case EGL_OPENGL_ES_API:
-            return eglGetProcAddress(name);
-        case EGL_NONE:
-            break;
-        }
 #endif
-    }
     errx(1, "Couldn't find current GLX or EGL context.\n");
-#endif
+
+    return NULL;
 }
 
 WRAPPER_VISIBILITY (void)