Add checks for netinet/ip.h and gai_strerror

Extracted from #745

Author: stephane

configure.ac

@@ -85,6 +85,7 @@ AC_CHECK_HEADERS([ \
     linux/serial.h \
     netdb.h \
     netinet/in.h \
+    netinet/ip.h \
     netinet/tcp.h \
     sys/ioctl.h \
     sys/params.h \
@@ -104,7 +105,7 @@ AC_CHECK_DECLS([__CYGWIN__])
 AC_SEARCH_LIBS(accept, network socket)
 
 # Checks for library functions.
-AC_CHECK_FUNCS([accept4 getaddrinfo gettimeofday inet_pton inet_ntop select socket strerror strlcpy])
+AC_CHECK_FUNCS([accept4 gai_strerror getaddrinfo gettimeofday inet_pton inet_ntop select socket strerror strlcpy])
 
 # Required for MinGW with GCC v4.8.1 on Win7
 AC_DEFINE(WINVER, 0x0501, _)