Harvey Kwok observes that EnumPrinters() can sometimes fail to fill

in its output parameters. Hence, we initialise them before calling
it.

[originally from svn r7729]

windows/winprint.c

@@ -21,7 +21,7 @@ struct printer_job_tag {
 static char *printer_add_enum(int param, DWORD level, char *buffer,
                               int offset, int *nprinters_ptr)
 {
-    DWORD needed, nprinters;
+    DWORD needed = 0, nprinters = 0;
 
     buffer = sresize(buffer, offset+512, char);