Report (and free) err_info for WTAP_ERR_DECOMPRESS.

Change-Id: I61ecc58be4b0688c43df0b0f006fb899bdc1721c
Reviewed-on: https://code.wireshark.org/review/4216
Reviewed-by: Guy Harris <guy@alum.mit.edu>
(cherry picked from commit be7f0539848238627db0e18acdc2dae5715c3182)
Reviewed-on: https://code.wireshark.org/review/4217