Add file selector widget to textscreen library.

Subversion-branch: /trunk/chocolate-doom
Subversion-revision: 2570
Fix file selector issues with Windows build.

Subversion-branch: /trunk/chocolate-doom
Subversion-revision: 2571
Change WAD selectors in setup tool to file selection widgets.

Subversion-branch: /trunk/chocolate-doom
Subversion-revision: 2572
Don't hog the CPU while waiting for the file selector.

Subversion-branch: /trunk/chocolate-doom
Subversion-revision: 2573
Allow backspace or delete to clear the contents of an input box.

Subversion-branch: /trunk/chocolate-doom
Subversion-revision: 2574
Add back call to TXT_Delay to fix OS X freeze.

Subversion-branch: /trunk/chocolate-doom
Subversion-revision: 2575
Fix Doxygen comments.

Subversion-branch: /trunk/chocolate-doom
Subversion-revision: 2576