Update error.cpp

When compiling with g++ (GCC) 4.4.7 20120313 (Red Hat 4.4.7-18) an error occurs: 
error.cpp: In member function ‘void Error::generate_error(unsigned int, std::string, std::string)’:
error.cpp:146: error: ‘exit’ was not declared in this scope
The fix is to include the #include <cstdlib> where the exit() function is decleared in the error.cpp file

tools/pymol_asphere/src/error.cpp

@@ -13,7 +13,8 @@
 
 #include "error.h"
 #include <cstring>
- 
+#include <cstdlib>
+
 Notice::Notice() {
 	nullout=new ostream(NULL);
 	noteout=&cout;