Backend abstraction + added android support + partial high DPI scaling + added missing files

core/backends/android/keybinds.h

@@ -0,0 +1,27 @@
+#pragma once
+
+// No keyboard controls
+#define KB_KEY_HOME         -1
+#define KB_KEY_MENU         -1
+#define KB_KEY_END          -1
+#define KB_KEY_ESC          -1
+#define KB_KEY_PG_UP        -1
+#define KB_KEY_PG_DOWN      -1
+
+#define KB_KEY_ENTER        -1
+#define KB_KEY_KP_ENTER     -1
+#define KB_KEY_DEL          -1
+#define KB_KEY_BACKSPACE    -1
+
+#define KB_KEY_LEFT         -1
+#define KB_KEY_RIGHT        -1
+#define KB_KEY_UP           -1
+#define KB_KEY_DOWN         -1
+
+#define KB_KEY_LCTRL        -1
+#define KB_KEY_RCTRL        -1
+#define KB_KEY_LSHIFT       -1
+#define KB_KEY_RSHIFT       -1
+
+#define KB_KEY_A            -1
+#define KB_KEY_R            -1