OT_TOOL_PACKED_FIELD macro

@def OT_TOOL_PACKED_BEGIN Compiler-specific indication that a class or struct must be byte packed. @def OT_TOOL_PACKED_FIELD Indicate to the compiler a nested struct or union to be packed within byte packed class or struct. @def OT_TOOL_PACKED_END Compiler-specific indication at the end of a byte packed class or struct. @def OT_TOOL_WEAK Compiler-specific weak symbol modifier. @def OT_TOOL_PRINTF_STYLE_FORMAT_ARG_CHECK Specifies that a function or method takes `printf` style arguments and should be type-checked against a format string. Must be added after the function/method declaration. For example: `void MyPrintf(void *aObject, const char *aFormat, ...) OT_TOOL_PRINTF_STYLE_FORMAT_ARG_CHECK(2, 3);` The two argument index values indicate format string and first argument to check against it. They start at index 1 for the first parameter in a function and at index 2 for the first parameter in a method.