Pass CMake variables as compiler definitions using config.h.in

[Eyal Rozenberg]

Instead of writing:

set_property(TARGET dbgen qgen APPEND PROPERTY COMPILE_DEFINITIONS ${DATABASE} ${WORKLOAD})

(and if-set-endif statements for conditional defines, like we would need for issue #26 ) - let's just use our cmake.h.in mechanism with #define @VARNAME_HERE@ and #cmakedefine directives.

[Eyal Rozenberg]

Fixed by commit a621655.