Avoid using eglGPA() for core funcs when the current context is GLX.

If you already had GLX loaded by epoxy, this wouldn't happen, but on
the first call, fallback cases might have taken the EGL path if EGL
was loaded.

src/dispatch_common.c

@@ -517,6 +517,11 @@ epoxy_get_proc_address(const char *name)
 #else
     if (api.glx_handle && glXGetCurrentContext()) {
         return glXGetProcAddressARB((const GLubyte *)name);
+#if PLATFORM_HAS_EGL
+    } else if (api.egl_handle &&
+               epoxy_egl_get_current_gl_context_api() != EGL_NONE) {
+        return eglGetProcAddress(name);
+#endif /* PLATFORM_HAS_EGL */
     } else {
         /* If the application hasn't explicitly called some of our GLX
          * or EGL code but has presumably set up a context on its own,
@@ -536,7 +541,7 @@ epoxy_get_proc_address(const char *name)
 
 #if PLATFORM_HAS_EGL
         egl_gpa = dlsym(NULL, "eglGetProcAddress");
-        if (egl_gpa)
+        if (egl_gpa && epoxy_egl_get_current_gl_context_api() != EGL_NONE)
             return egl_gpa(name);
 #endif /* PLATFORM_HAS_EGL */
 
@@ -552,7 +557,7 @@ epoxy_get_proc_address(const char *name)
 #if PLATFORM_HAS_EGL
         egl_gpa = do_dlsym(&api.egl_handle, "libEGL.so.1", "eglGetProcAddress",
                            false);
-        if (egl_gpa)
+        if (egl_gpa && epoxy_egl_get_current_gl_context_api() != EGL_NONE)
             return egl_gpa(name);
 #endif /* PLATFORM_HAS_EGL */