(svn r1585) Rewrite CmdBuildSignals()
This addresses several issues:
- Correct comments
- Check input parameters for validity (and don't assert() them)
- Reorder checks if action is possible to produce more meaningful error messages
- Correct bug where money was charged for an action which should be free
- Kill warning about uninitialized variable, because the variable exists no more
- Make more clear how the function works (at least i hope so)

//{{NO_DEPENDENCIES}}
// Microsoft Developer Studio generated include file.
// Used by ttd.rc
//

// Next default values for new objects
//
#ifdef APSTUDIO_INVOKED
#ifndef APSTUDIO_READONLY_SYMBOLS
#define _APS_NEXT_RESOURCE_VALUE        104
#define _APS_NEXT_COMMAND_VALUE         40001
#define _APS_NEXT_CONTROL_VALUE         1005
#define _APS_NEXT_SYMED_VALUE           101
#endif
#endif