add dependency requirements for CentOS/RedHat
fix README.cygwin

"perl Makefile.PL" currently by default builds with X11 libraries,
not with Windows libraries. Changed README to reflect the current
situation.
Tk::Table documentation: mention -takefocus => 0

The current default (-takefocus => 1 with the custom
FocusChildren() implementation) means that embedded widgets don't get
the focus during keyboard traversal. Explicitely document how to fix
this.

Change inspired by this question on StackOverflow:
http://stackoverflow.com/questions/19978616/perl-tk-tab-between-entry-widgets
new test script sv.t

This test script currently contains a test case for RT #90077.
fix for RT #90077