Fix build warning in jerry-ext/arg on tizenrt-artik05x

[glistening]

tizenrt-arttik05x treats warning as error for uninitialized use.
This patch fixes the error in jerry-ext/arg by initializing to zero.

JerryScript-DCO-1.0-Signed-off-by: Sanggyu Lee sg5.lee@samsung.com

[yichoi]

LGTM

[glistening]

Here is error log.

/home/brian/iotjs/jerry-tizenrt/jerryscript/jerry-ext/arg/arg-transform-functions.c: In function 'jerryx_arg_transform_uint8_strict':
/home/brian/iotjs/jerry-tizenrt/jerryscript/jerry-ext/arg/arg-transform-functions.c:151:41: error: 'tmp' may be used uninitialized in this function [-Werror=maybe-uninitialized]
     *d = (*d >= 0.0) ? floor (*d + 0.5) : ceil (*d - 0.5);
                                         ^
/home/brian/iotjs/jerry-tizenrt/jerryscript/jerry-ext/arg/arg-transform-functions.c:172:12: note: 'tmp' was declared here
     double tmp; \
            ^
/home/brian/iotjs/jerry-tizenrt/jerryscript/jerry-ext/arg/arg-transform-functions.c:190:3: note: in expansion of macro 'JERRYX_ARG_TRANSFORM_FUNC_FOR_INT_TEMPLATE'
   JERRYX_ARG_TRANSFORM_FUNC_FOR_INT_TEMPLATE (type, _strict, min, max) \
   ^
/home/brian/iotjs/jerry-tizenrt/jerryscript/jerry-ext/arg/arg-transform-functions.c:193:1: note: in expansion of macro 'JERRYX_ARG_TRANSFORM_FUNC_FOR_INT'
 JERRYX_ARG_TRANSFORM_FUNC_FOR_INT (uint8, 0, UINT8_MAX)