Fix: compat: include common/macros.h in mman.h

Fix: compat: include common/macros.h in mman.h

When building on Windows, this mman.h must include common/macros.h to
see the definition of BT_EXTERN_C.  The build works in current master,
but I got some build failures that uncovered this problem which working
on some unrelated changes.

Change-Id: Ia81714d6d278724a0bc1fd20817e675f0167f2a1
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/8661
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>
Tested-by: jenkins <jenkins@lttng.org>