#170 dialog default button doesn't work

[Derek Noonburg]

Hitting <return> in a FormDialog doesn't activate the
default button if the current focus is on a TextField
widget. (Hitting <escape> in this situation correctly
activates the cancel button.)

This can be reproduced with xpdf 2.00
(ftp://ftp.foolabs.com/pub/xpdf/xpdf-2.00.tar.gz),
using lesstif 0.93.36. Run xpdf, open the find dialog
(hit 'f'), enter a search string, and (leaving the
focus on the search string widget) hit <return>.

I have verified that this works correctly using OpenMotif.

The code that builds this dialog is in
xpdf/XpdfViewer.cc, in the XPDFViewer::initFindDialog()
function.