Merge pull request #4800 from assimp/kimkulling/add_missing_header_issue-4720

Add missing header for Ubuntu 16 and Mac

include/assimp/Hash.h

@@ -47,6 +47,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #endif
 
 #include <stdint.h>
+#include <stdlib.h>
 #include <string.h>
 #include <cmath>
 
@@ -64,11 +65,11 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #undef get16bits
 #if (defined(__GNUC__) && defined(__i386__)) || defined(__WATCOMC__) \
   || defined(_MSC_VER) || defined (__BORLANDC__) || defined (__TURBOC__)
-#define get16bits(d) (*((const uint16_t *) (d)))
+#  define get16bits(d) (*((const uint16_t *) (d)))
 #endif
 
 #if !defined (get16bits)
-#define get16bits(d) ((((uint32_t)(((const uint8_t *)(d))[1])) << 8)\
+#  define get16bits(d) ((((uint32_t)(((const uint8_t *)(d))[1])) << 8)\
                        +(uint32_t)(((const uint8_t *)(d))[0]) )
 #endif
 
@@ -77,8 +78,8 @@ inline uint32_t SuperFastHash (const char * data, uint32_t len = 0, uint32_t has
     uint32_t tmp;
     int rem;
     
-    if (!data) return 0;
-    if (!len)len = (uint32_t)::strlen(data);
+    if (data == NULL) return 0;
+    if (len == 0)len = (uint32_t)::strlen(data);
 
     rem = len & 3;
     len >>= 2;