Qt: KeyboardInputInterval - allow more relaxed typing for keyboardSearch

Gtk popped up a search box when typing in the tree view.
Most places in Qt, a Search: field was added to the dialog.
Looks possible to buffer keystrokes and do a string search in Qt.

Default value is 400ms (even on Windows). Average typing speed of
200 cpm = 300ms per character = too close to 400ms when searching
the protocol name in Preferences -> Protocols.

docbook/wsug_src/WSUG_chapter_customize.adoc

@@ -631,7 +631,7 @@ side is a tree where you can select the page to be shown.
 image::wsug_graphics/ws-gui-preferences.png[{screenshot-attrs}]
 
 Wireshark supports quite a few protocols, which is reflected in the long list of entries in the “Protocols” pane.
-You can jump to the preferences for a specific protocol by expanding “Protocols” and quickly typing the first few letters of the protocol name.
+You can jump to the preferences for a specific protocol by expanding “Protocols” and typing the first few letters of the protocol name.
 
 The “Advanced” pane will let you view and edit all of Wireshark’s preferences, similar to link:about:config[] and link:chrome:flags[] in the Firefox and Chrome web browsers.
 

ui/qt/main.cpp

@@ -651,6 +651,10 @@ int main(int argc, char *qt_argv[])
     /* Create The Wireshark app */
     WiresharkApplication ws_app(argc, qt_argv);
 
+    // Default value is 400ms = "quickly typing" when searching in Preferences->Protocols
+    // 1000ms allows a more "hunt/peck" typing speed. 2000ms tested - too long.
+    QApplication::setKeyboardInputInterval(1000);
+
     /* initialize the funnel mini-api */
     // xxx qtshark
     //initialize_funnel_ops();