Add pawn include files for GroupStatus.

line 188 -- // Ask if a user in in the specified group, results returns async by GSUserGroupStatus_t
line 190 -- virtual bool RequestUserGroupStatus( CSteamID steamIDUser, CSteamID steamIDGroup ) = 0;
line 333 -- // send as a reply to RequestUserGroupStatus()
line 334 -- struct GSClientGroupStatus_t

Why it's User then Client in the SDK is beyond me... :\

Pawn/includes/SteamWorks.inc

@@ -181,6 +181,8 @@ native bool:SteamWorks_IsConnected();
 native bool:SteamWorks_SetRule(const String:sKey[], const String:sValue[]);
 native bool:SteamWorks_ClearRules();
 native bool:SteamWorks_ForceHeartbeat();
+native bool:SteamWorks_GetUserGroupStatus(client, groupid);
+native bool:SteamWorks_GetUserGroupStatusAuthID(authid, groupid);
 
 native EUserHasLicenseForAppResult:SteamWorks_HasLicenseForApp(client, app);
 native SteamWorks_GetClientSteamID(client, String:sSteamID[], length);
@@ -251,6 +253,8 @@ forward SteamWorks_SteamServersDisconnected(EResult:result);
 forward Action:SteamWorks_RestartRequested();
 forward SteamWorks_TokenRequested(String:sToken[], maxlen);
 
+forward SteamWorks_OnClientGroupStatus(authid, groupid, bool:isMember, bool:isOfficer);
+
 public Extension:__ext_SteamWorks = 
 {
 	name = "SteamWorks",