custom channel flags and case-sensitivity #1907

When you create a custom channel flag, it's case insensitive:

.tcl setudef dummy
.tcl setudef DuMmY
.tcl setudef DUMMY

These 3 commands will only create the dummy flag (the first created)

Doing .chanset #mychan +dUmMy works whatever is the case of the dummy flag.

.tcl channel get #mychan dUmMy will result Tcl error: Unknown channel setting.

bind chanset - dUmMy will never trigger.