[Keymap] Various enhancements for dshields user space and keymaps. (#6816)

- Add oneshot mod/layer unlocking
- Fix Planck rev 3 backlight breathing
- Fix Planck rev 6 build with arm gcc 9.2.0
- General code clean up

users/dshields/dshields.c

@@ -1,30 +1,31 @@
-extern keymap_config_t keymap_config;
+#include "quantum.h"
+#include "dshields.h"
 
-/* uncomment to reset
-void matrix_init_user(void) {
-    eeconfig_init();
-};
-*/
+extern bool process_record_dynamic_macro(uint16_t keycode, keyrecord_t *record);
 
 bool process_record_user(uint16_t keycode, keyrecord_t *record) {
     if (!process_record_dynamic_macro(keycode, record)) {
         return false;
     }
+    if (keycode == KC_ESC && record->event.pressed) {
+        bool rc = true;
+        uint8_t mods = 0;
+        if ((mods = get_oneshot_mods()) && !has_oneshot_mods_timed_out()) {
+            clear_oneshot_mods();
+            unregister_mods(mods);
+            rc = false;
+        }
+        if ((mods = get_oneshot_locked_mods())) {
+            clear_oneshot_locked_mods();
+            unregister_mods(mods);
+            rc = false;
+        }
+        if (is_oneshot_layer_active()) {
+            layer_clear();
+            rc = false;
+        }
+        return rc;
+    }
     return true;
 }
 
-// work in progress
-uint32_t layer_state_set_user(uint32_t state) {
-    switch (biton32(state)) {
-        case DEF:
-            set_all_leds_to(0,0,0);
-            break;
-        case FUN:
-            // TODO light the fn keys
-            // set_led_to(?, 0, 128, 0);
-            // set_led_to(?, 0, 128, 0);
-            break;
-    }
-    return state;
-}
-