Adapt the daqd parser to work with new/old flex

With flex <= 2.5 yyin/yyout are pointers, with 2.6+ they are member
objects of the generated lexer.  Adapt the build system to detect which
is in use, and the code to work with both variants in flex.

Among other items allows daqd to build on both Debian 8 & 9.

git-svn-id: https://redoubt.ligo-wa.caltech.edu/svn/advLigoRTS/trunk@4538 6dcd42c9-f523-4c6d-aada-af552506706e