refactor: replace filename hyphens with underscores

Aligns *.h and *.c to underscore naming convention.

These were kept (with warnings) for backwards compatibility with external boards/shields:
- kscan-mock.h
- matrix-transform.h
They should be removed in the future.

PR: #523

app/include/zmk/events/keycode_state_changed.h

@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2020 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#pragma once
+
+#include <zephyr.h>
+#include <dt-bindings/zmk/modifiers.h>
+#include <dt-bindings/zmk/hid_usage_pages.h>
+#include <zmk/event_manager.h>
+#include <zmk/keys.h>
+
+struct keycode_state_changed {
+    struct zmk_event_header header;
+    uint8_t usage_page;
+    uint32_t keycode;
+    uint8_t implicit_modifiers;
+    bool state;
+    int64_t timestamp;
+};
+
+ZMK_EVENT_DECLARE(keycode_state_changed);
+
+static inline struct keycode_state_changed *
+keycode_state_changed_from_encoded(uint32_t encoded, bool pressed, int64_t timestamp) {
+    uint16_t page = HID_USAGE_PAGE(encoded) & 0xFF;
+    uint16_t id = HID_USAGE_ID(encoded);
+    zmk_mod_flags implicit_mods = SELECT_MODS(encoded);
+
+    if (!page) {
+        page = HID_USAGE_KEY;
+    }
+
+    struct keycode_state_changed *ev = new_keycode_state_changed();
+    ev->usage_page = page;
+    ev->keycode = id;
+    ev->implicit_modifiers = implicit_mods;
+    ev->state = pressed;
+    ev->timestamp = timestamp;
+    return ev;
+}