Ensure that const and pure function attributes are used properly (#1739)

Some functions were incorrectly marked as const but were pure only
(or not even pure). Some functions were marked as pure but
qualified as const. Some functions were not attributed at all but
qualified either as pure or const. Some functions had attributes
at definition but not at declaration. This commit fixes these
inconsistencies.

JerryScript-DCO-1.0-Signed-off-by: Akos Kiss akiss@inf.u-szeged.hu

jerry-core/jmem/jmem-allocator.c

@@ -56,7 +56,7 @@ jmem_finalize (void)
  *
  * @return packed pointer
  */
-inline jmem_cpointer_t __attr_always_inline___
+inline jmem_cpointer_t __attr_pure___ __attr_always_inline___
 jmem_compress_pointer (const void *pointer_p) /**< pointer to compress */
 {
   JERRY_ASSERT (pointer_p != NULL);
@@ -90,7 +90,7 @@ jmem_compress_pointer (const void *pointer_p) /**< pointer to compress */
  *
  * @return unpacked pointer
  */
-inline void * __attr_always_inline___
+inline void * __attr_pure___ __attr_always_inline___
 jmem_decompress_pointer (uintptr_t compressed_pointer) /**< pointer to decompress */
 {
   JERRY_ASSERT (compressed_pointer != JMEM_CP_NULL);