while we are fixing c++ compatibility
some headers with function prototypes
do not have extern "C" block for c++

extern "C" block ending is wrong in
pty.h

extern "C" block is missing from
arpa/inet.h
alloca.h
ftw.h
math.h
net/if.h
netinet/in.h
sys/mount.h
sys/msg.h
sys/resource.h
sys/shm.h
sys/statfs.h
sys/statvfs.h
sys/swap.h
sys/sysctl.h
sys/sysinfo.h
sys/times.h
sys/uio.h
sys/utsname.h