fix FreeBSD compile issue.

alloca is defined in stdlib.h on [freeBSD](https://www.freebsd.org/cgi/man.cgi?alloca)

additional fix to 75c1314ab0

src/lib/sw_engine/tvgSwRaster.cpp

@@ -19,6 +19,15 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  */
+
+#ifdef _WIN32
+    #include <malloc.h>
+#elif __FreeBSD__
+    #include<stdlib.h>
+#else
+    #include <alloca.h>
+#endif
+
 #include "tvgMath.h"
 #include "tvgRender.h"
 #include "tvgSwCommon.h"

src/loaders/tvg/tvgTvgBinInterpreter.cpp

@@ -23,6 +23,8 @@
 
 #ifdef _WIN32
     #include <malloc.h>
+#elif __FreeBSD__
+    #include<stdlib.h>
 #else
     #include <alloca.h>
 #endif

src/savers/tvg/tvgTvgSaver.cpp

@@ -28,6 +28,8 @@
 
 #ifdef _WIN32
     #include <malloc.h>
+#elif __FreeBSD__
+    #include<stdlib.h>
 #else
     #include <alloca.h>
 #endif