Make ODBC configure handle OS X Mavericks and Yosemite

OS X Mavericks is based on Darwin version 13.x, and Yosemite on
14.x. Change the ODBC configure.in script to recognize these versions.
Merge branch 'vinoski/darwin-vsn-odbc' into maint

* vinoski/darwin-vsn-odbc:
  Make ODBC configure handle OS X Mavericks and Yosemite
Merge branch 'maint'