Replace IPv6 colons in access-log filenames with exclaimation marks on Windows

Colons are not legal filename characters on Windows and when virtual hosts are
enabled, the IPv6 address of the server may be used in the access-log filename
so we need to clean that up or errors opening/creating the access-log files
occur.

src/sbbs3/websrvr.c

@@ -6960,8 +6960,14 @@ void http_logging_thread(void* arg)
 		}
 		SAFECOPY(newfilename,base);
 		if((startup->options&WEB_OPT_VIRTUAL_HOSTS) && ld->vhost!=NULL) {
-			SAFECAT(newfilename,ld->vhost);
-			if(ld->vhost[0])
+			char vhost[128];
+			SAFECOPY(vhost, ld->vhost);
+#ifdef _WIN32
+			char* p;
+			REPLACE_CHARS(vhost, ':', '!', p);
+#endif
+			SAFECAT(newfilename,vhost);
+			if(vhost[0])
 				SAFECAT(newfilename,"-");
 		}
 		strftime(strchr(newfilename,0),15,"%Y-%m-%d.log",&ld->completed);