Add EGL-based backend for wxGLCanvas

Among other things, this enables wxGLCanvas to be used natively on
Wayland.

Closes https://github.com/wxWidgets/wxWidgets/pull/2038

Closes #17702.

configure.in

@@ -3793,6 +3793,18 @@ if test "$wxUSE_OPENGL" = "yes" -o "$wxUSE_OPENGL" = "auto"; then
 
                         found_gl=1
                         OPENGL_LIBS="-lGL -lGLU"
+
+                        if test "$WXGTK3" = 1; then
+                            PKG_CHECK_MODULES(EGL, [egl >= 1.5],
+                                [
+                                    OPENGL_LIBS="$OPENGL_LIBS $EGL_LIBS"
+                                    AC_DEFINE(wxUSE_GLCANVAS_EGL)
+                                ],
+                                [
+                                    AC_MSG_NOTICE([EGL 1.5+ not available. Will use GLX.])
+                                ]
+                            )
+                        fi
                     fi
                 fi