Fix undefined references build errors on Windows (#3004)

We should emit function symbols for ecma_date_day, ecma_is_value_string and
ecma_number_is_nan inline functions, because they are used by unit tests:
unit-core/test-date-helpers.c, test-literal-storage.c and test-string-to-number.c.

JerryScript-DCO-1.0-Signed-off-by: Csaba Osztrogonác oszi@inf.u-szeged.hu

jerry-core/ecma/builtin-objects/ecma-builtin-helpers-date.c

@@ -41,7 +41,7 @@
  *
  * @return time value for day number
  */
-inline ecma_number_t JERRY_ATTR_ALWAYS_INLINE
+extern inline ecma_number_t JERRY_ATTR_ALWAYS_INLINE
 ecma_date_day (ecma_number_t time) /**< time value */
 {
   JERRY_ASSERT (!ecma_number_is_nan (time));