Separate out the lextest so that it is run by "make" and "make install".

Separate out the lextest so that it is run by "make" and "make install".
 Before, "make install" did not run the lextest.
Fix up the ODBC make from this main configure.
Include configure test for "ln -s" in Makefile.global.in.
 Was always in configure, just not carried through to here for use.