Elements tested:
```
TESTING_FAIL_INIT      = 1 << 0,   // Initialization (InitWindow())    -> "INFO: DISPLAY: Device initialized successfully"
            TESTING_FAIL_CLOSE     = 1 << 1,   // Closing (CloseWindow())          -> "INFO: Window closed successfully"
            TESTING_FAIL_ASSETS    = 1 << 2,   // Assets loading (WARNING: FILE:)  -> "WARNING: FILEIO:"
            TESTING_FAIL_RLGL      = 1 << 3,   // OpenGL-wrapped initialization    -> "INFO: RLGL: Default OpenGL state initialized successfully"
            TESTING_FAIL_PLATFORM  = 1 << 4,   // Platform initialization          -> "INFO: PLATFORM: DESKTOP (GLFW - Win32): Initialized successfully"
            TESTING_FAIL_FONT      = 1 << 5,   // Font default initialization      -> "INFO: FONT: Default font loaded successfully (224 glyphs)"
            TESTING_FAIL_TIMER     = 1 << 6,   // Timer initialization             -> "INFO: TIMER: Target time per frame: 16.667 milliseconds"
```

ADDED: Some log info

* FIXED: rexm's makefile and default paths

Fixed a windows only backslash in
rexm's makefile causing build errors on macOS and linux

Added unix paths to rexm for better compatibility

* Update rexm.c

Readded the fall-through in OP_CREATE

Added some safety checks to UpdateRequiredFiles() so it plays nicely outside of the raylib.com context (would segfault previously)