When building the graphviz port with the ruby plugin, the configure script fails to locate the ruby program.

The problem is that the configure script expects the ruby program to be named 'ruby'.  But the lang/ruby19 port installs the program as ruby19.

To fix this issue, I added RUBY=${RUBY} to CONFIGURE_ENV.  This then resulted in the configure script failing to find the ruby.h header files.  This is failing due to ruby19 now has the header files in the include dir instead of the lib directory.

Fix: The attached patch fixes these problem.

Changed files:
  Makefile
  files/patch-configure

NOTE: This patch hasn't been tested with lang/ruby18.

Patch attached with submission follows:
How-To-Repeat: Install lang/ruby19
# cd /usr/ports/graphics/graphviz
# make clean ; make config

  Choose the RUBY option

# make install
# pkg_info -g `make -V PKGNAME`
Information for graphviz-2.26.3_3:

Mismatched Checksums:
pkg_info: /usr/local/man/man3/gv.3ruby.gz doesn't exist
pkg_info: /usr/local/lib/graphviz/ruby/gv.so doesn't exist
pkg_info: /usr/local/lib/graphviz/ruby/libgv_ruby.a doesn't exist
pkg_info: /usr/local/lib/graphviz/ruby/libgv_ruby.la doesn't exist
pkg_info: /usr/local/lib/graphviz/ruby/libgv_ruby.so doesn't exist
pkg_info: /usr/local/lib/ruby/site_ruby/1.9/amd64-freebsd9/gv.so doesn't exist
pkg_info: /usr/local/share/graphviz/demo/modgraph.rb doesn't exist