xconfig Help mentions 'Show Debug Info' but it was missing from any
menu.
* Add 'Show debug' menu to the main menu.
* Properly load showDebug settings.
Reported-by: Jason Vas Dias <jason.vas.dias@gmail.com> Signed-off-by: Boris Barbulovski <bbarbulovski@gmail.com> Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Tested-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Michal Marek <mmarek@suse.com>