Fix bug #1213411: Linux kernel module: NULL pointer dereferences
Fix bug #1213411: Linux kernel module: NULL pointer dereferences

The rohc_test.ko module throws multiple NULL-pointer dereference oopses
in kernel log during the test.

The problem is related to the way the ROHC compressor/decompressor
couples are created and destroyed in the rohc_test.ko module. Upon the
first /proc open, the couples are created. They are also released upon
the first /proc close. However, some other /proc may still be used and
ask the rohc_test.ko module to perform some compression/decompression.

This change replaces the boolean that indicates whether the couples were
created or not by a counters of references.

This change is related to a problem reported by Mikhail Gruzdev on the
ROHC mailing list. See https://bugs.launchpad.net/rohc/+bug/1213411

didier-barvaux/rohc,didier-barvaux/rohc,didier-barvaux/rohc,didier-barvaux/rohc,didier-barvaux/rohc