progsig: Fix remove and clone program functions being completely broken.

Remove function only removed instructions from the local machine, and
was therefore not MP safe.
Clone function failed to work correctly for non-trivial cases,
and sometimes caused an array out of bounds assertion.

These are replaced by a new commandproc which does each operation
as a single action, which is therefore MP safe.

Remove an unused struct field.

src/command_type.h

@@ -332,6 +332,7 @@ enum Commands {
 	CMD_INSERT_SIGNAL_INSTRUCTION,    ///< insert a signal instruction
 	CMD_MODIFY_SIGNAL_INSTRUCTION,    ///< modifies a signal instruction
 	CMD_REMOVE_SIGNAL_INSTRUCTION,    ///< removes a signal instruction
+	CMD_SIGNAL_PROGRAM_MGMT,          ///< removes a signal program management command
 
 	CMD_END,                          ///< Must ALWAYS be on the end of this list!! (period)
 };