During role/race/gender/alignment selection, when gender gets toggled
replace the gender-specific role titles and their icons to reflect
new gender value. And enable or disable Valkyrie choice depending
upon the gender value, not just current race value.
This ended up revising a lot of the NetHackQtPlayerSelector code,
eliminating some redundancies and being more careful with the use of
validrace()/validgend()/validalign(). That still isn't bulletproof.
It also changes the two instances of buttonPressed that were drawing
Qt6 warnings from connect() at run-time with buttonClicked. That
works as intended with Qt5 and might eliminate those.
The code to use female player character tiles looks correct to me
but when I toggle gender, role titles change but their icons don't.
I don't know what's going on here. Some ealier code always specifies
MALE but that code isn't used according to various prints to stderr
that I temporarily inserted.
For Qt's character selection widget, only allow the [Play] button
to be used when the character name field is non-blank. When that
field is blank, show "(required)" there.
Catch up with SYSCF for checking generic names like "player".
Fix up handling for some conditionally unused variables.
