Log Message:
cad/openscad: Use wrappers for bison, USE_TOOLS-= flex

On DragonFly, the path for bison and lex were set to /usr/local/bin/bison
and /usr/local/bin/flex.  These were basically hardcoded.  The added
patches set the paths to "bison" and "flex" which pick up the
${WRKDIR}/.tools/bin/ and ${PREFIX}/bin versions instead.

flex was removed from USE_TOOLS because the pkgsrc FlexLexer.h can build
openscad and the one that comes with DragonFly can't.  It was replaced
with the flex buildlink3 and it should work everywhere.