Uninline Toplevel::pid()

It's only used from one method and requires to have NETWinInfo being
included in the header.

toplevel.cpp

@@ -487,6 +487,11 @@ void Toplevel::elevate(bool elevate)
     effectWindow()->elevate(elevate);
 }
 
+pid_t Toplevel::pid() const
+{
+    return info->pid();
+}
+
 } // namespace
 
 #include "toplevel.moc"

toplevel.h

@@ -655,11 +655,6 @@ inline QByteArray Toplevel::windowRole() const
     return window_role;
 }
 
-inline pid_t Toplevel::pid() const
-{
-    return info->pid();
-}
-
 inline bool Toplevel::unredirected() const
 {
     return unredirect;