Add new command line option -singlestep for tcg single stepping.

Add new command line option -singlestep for tcg single stepping.

This replaces a compile time option for some targets and adds
this feature to targets which did not have a compile time option.

Add monitor command to enable or disable single step mode.

Modify monitor command "info status" to display single step mode.

Signed-off-by: Stefan Weil <weil@mail.berlios.de>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@7004 c046a42c-6fe2-441c-8c8c-71466251a162