Allow adding new variables in the var sheet

[pspp] / src / ui / gui / psppire.gtkrc

#
# Avoid making buttons inside the PSPPIRE data sheet and variable sheet
# extra-tall.  This allows more rows to fit on the screen, making data
# easier to review.
#
style "thinbuttons" { ythickness = 0 }
widget_class "*<PsppSheetView>*GtkButton" style : rc "thinbuttons"