[Shared] Set CPU affinity on com_affinity modify

CPU affinity of the current process is now updated when com_affinity is
changed, instead of only on startup. Setting com_affinity to 0 now means
use all cores instead of "do nothing", which does not work now that the
affinity can be updated at run-time.

code/qcommon/common.cpp

@@ -1497,6 +1497,12 @@ void Com_Frame( void ) {
 			c_pointcontents = 0;
 		}
 
+		if ( com_affinity->modified )
+		{
+			com_affinity->modified = qfalse;
+			Sys_SetProcessorAffinity();
+		}
+
 		com_frameNumber++;
 	}
 	catch ( int code )

codemp/qcommon/common.cpp

@@ -1575,6 +1575,12 @@ void Com_Frame( void ) {
 			c_pointcontents = 0;
 		}
 
+		if ( com_affinity->modified )
+		{
+			com_affinity->modified = qfalse;
+			Sys_SetProcessorAffinity();
+		}
+
 		com_frameNumber++;
 	}
 	catch (int code) {

shared/sys/sys_unix.cpp

@@ -487,10 +487,10 @@ void Sys_SetProcessorAffinity( void ) {
 	if ( sscanf( com_affinity->string, "%X", &cores ) != 1 )
 		cores = 1; // set to first core only
 
+	const long numCores = sysconf( _SC_NPROCESSORS_ONLN );
 	if ( !cores )
-		return;
+		cores = (1 << numCores) - 1; // use all cores
 
-	const long numCores = sysconf( _SC_NPROCESSORS_ONLN );
 	cpu_set_t set;
 	CPU_ZERO( &set );
 	for ( int i = 0; i < numCores; i++ ) {

shared/sys/sys_win32.cpp

@@ -178,17 +178,20 @@ static const char *GetErrorString( DWORD error ) {
 }
 
 void Sys_SetProcessorAffinity( void ) {
-	DWORD_PTR processMask, dummy;
+	DWORD_PTR processMask, processAffinityMask, systemAffinityMask;
 	HANDLE handle = GetCurrentProcess();
 
-	if ( !GetProcessAffinityMask( handle, &dummy, &dummy ) )
+	if ( !GetProcessAffinityMask( handle, &processAffinityMask, &systemAffinityMask ) )
 		return;
 
 	if ( sscanf( com_affinity->string, "%X", &processMask ) != 1 )
 		processMask = 1; // set to first core only
 
 	if ( !processMask )
-		return;
+		processMask = systemAffinityMask; // use all the cores available to the system
+
+	if ( processMask == processAffinityMask )
+		return; // no change
 
 	if ( !SetProcessAffinityMask( handle, processMask ) )
 		Com_DPrintf( "Setting affinity mask failed (%s)\n", GetErrorString( GetLastError() ) );