Deprecated and dangerous autoconf idiom that checks for a type that
isn't used anywhere in the source and breaks the inclusion of
<netinet/in.h>.

--- configure.in.orig	Fri Feb  3 17:10:04 2017
+++ configure.in	Fri Feb  3 17:15:48 2017
@@ -67,7 +67,6 @@ AC_CHECK_TYPE(u_int64_t, unsigned long long)
 AC_CHECK_TYPE(u_int32_t, unsigned int)
 AC_CHECK_TYPE(u_int16_t, unsigned short)
 AC_CHECK_TYPE(u_int8_t, unsigned char)
-AC_CHECK_TYPE(in_addr_t, unsigned long)
 
 dnl Checks for library functions.
 AC_PROG_GCC_TRADITIONAL