Added some missing #includes whose prevent build source with gcc 4.3


git-svn-id: svn://svn.code.sf.net/p/tigervnc/code/trunk@2431 3789f03b-4d11-0410-bbf8-ca57d06f2519
diff --git a/unix/tx/TXImage.cxx b/unix/tx/TXImage.cxx
index 5fa6828..95cd2b7 100644
--- a/unix/tx/TXImage.cxx
+++ b/unix/tx/TXImage.cxx
@@ -21,6 +21,7 @@
 
 
 #include <stdio.h>
+#include <stdlib.h>
 #include <strings.h>
 #include <sys/types.h>
 #include <sys/ipc.h>