fix: cast malloc result and adjust compiler emit functions for C++ compatibility

- Cast malloc return to char* in src/main.c to avoid C++ implicit void* conversion
- Rename emit to emitByteArg and emitShort to emitShortArg in src/wren_compiler.c to avoid conflict with new emit and emitShort helpers
- Add new emit function taking uint8_t byte and emitShort helper for 16-bit big-endian emission
- Remove stray semicolon in script/test.py

script/test.py

@@ -42,7 +42,7 @@ else:
 passed = 0
 failed = 0
 skipped = defaultdict(int)
-num_skipped = 0;
+num_skipped = 0
 
 
 def walk(dir, callback):