Add a script as a front-end for Flex, to work around various problems,

Add a script as a front-end for Flex, to work around various problems,
such as the fact that Flex strips all but the last component of the "-o"
argument, and that it doesn't generate a header file to declare routines
the generated lexical analyzer defines.  Use that script when building
lexical analyzers, and, for each lexical analyzer, include the generated
header file in the generated analyzer.

svn path=/trunk/; revision=22446