Do The Right Thing. (R)

Overall changes:
Use tabs instead of sequential spaces.
Note Author as well as WWW in DESCR.
Do not install examples when NOPORTDOCS.
Make RUBY, RUBY_VER and RUBY_ARCH variables overridable.

ruby-date2:
share/doc/ruby/date2/examples/ -> share/examples/ruby/date2/cal.rb

textproc/ruby-html-parser:
databases/ruby-mysql:
devel/ruby-optparse:
devel/ruby-property:
Install modules under lib/ruby/site_ruby/${RUBY_VER}/ instead
of lib/ruby/site_ruby/ or lib/ruby/${RUBY_VER}/

textproc/ruby-rdtool:
Install documents in .rd format too.
Format optparse's rd file. (Since ruby-rdtool depends on
optparse, it cannot be done during optparse's build
process. So ruby-rdtool should take care of that when it is
installed. :)