The gethostbyaddr code in system/netd now expects a string address
from inet_ntop, not raw bytes, in order to properly pass addresses
containing null and probably spaces and newlines characeters as well.
Bug: 4344448
git cherry-pick -e c13fa640eea3285a586fc4bad0abf2fc1b902185
Also add missing declarations to misc. functions.
Fix clearerr() implementation (previous was broken).
Handle feature test macros like _POSIX_C_SOURCE properly.
Change-Id: Icdc973a6b9d550a166fc2545f727ea837fe800c4