Fix displaying of title and buttons in different modes

[mfs12]

Description

• The message box title displays the R value from the previous M291 command (even if it was in a different macro). Verified with S = 0,1,2 but didn't test on other modes.
• If S = 1, there is no CLOSE button, but there is window close button ("X" in the corner). - reported by @Exerqtor
• If S=2, there is no OK button, but there is window close button ("X" in the corner). If T=0, the X will close the window but does not unblock execution. An INFO message is added to the eventlog saying "M292: cancelled=false"

[mfs12]

#293