Added lex to tools list
Added lex to tools list

This allows scons to set the other lex variables and accept our
lex parameter as an override. Without this change, flex still
needed to be in the system path for this to happen.

Signed-off-by: Frank Quinn <8e90d92b6718ce33106d66386b493961926d3d82@gmail.com>

fquinner/OpenMAMA,fquinner/OpenMAMA,fquinner/OpenMAMA,fquinner/OpenMAMA,fquinner/OpenMAMA,fquinner/OpenMAMA,fquinner/OpenMAMA