Poppler removed memCheck and gMemReport functions

Poppler removed memCheck and gMemReport functions

Only use gMemReport and memCheck functions if poppler version less
than 0.69.0

The poppler project removed the memCheck and gMemReport functions in
commits c362ab1b97f20c5b73b3bad8d52015f679178748 - Remove DEBUG_MEM
from Object since this uses RAII now and hence cannot leak.
(The existing tracking also is not thread-safe and hence unreliable.)

and

f89446f6917a869b0f1a80fcc8ce81a7213dade4 - Remove generic heap debugging
from gmem since external tools and compiler instrumentation achieve the
same effect.

This commit solves https://github.com/OpenPrinting/cups-filters/issues/62

Signed-off-by: Olivier Schonken <olivier.schonken@gmail.com>