build: include pthread.h since we use pthread-stuff in here
build: include pthread.h since we use pthread-stuff in here

Thanks to Michael Sioutis <papito.dit@gmail.com>

zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb