Reduce compilator warnings

warning: cast from 'const guint8 *' (aka 'const unsigned char *') to
	'const guint16 *' (aka 'const unsigned short *') increases required
	alignment from 1 to 2 [-Wcast-align]
warning: cast from 'const guint8 *' (aka 'const unsigned char *') to
	'const struct logger_entry *' increases required alignment
	from 1 to 4 [-Wcast-align]

Change-Id: I1ef8bfedb31c3f633166405689d8d788d45365db
Reviewed-on: https://code.wireshark.org/review/4236
Petri-Dish: Michal Labedzki <michal.labedzki@tieto.com>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Tested-by: Michal Labedzki <michal.labedzki@tieto.com>
Reviewed-by: Michal Labedzki <michal.labedzki@tieto.com>