Update debugger button states at startup to disable non-functional JIT menu items

There is a bug with the JIT menu items: they are not disabled at startup, even though the JIT isn't initialized at the time. When someone toggles an item (e.g. JIT LoadStore Off) before loading a game, the checkbox is checked, but the option isn't actually enabled, and will not be enabled once a game is loaded.

This patch calls the update button states function after the main window is created to allow the debugger to disable non-functional menu items and buttons.