build: drop the inet_pton gnulib module

All use of this function was purged a long time ago in favour
of getaddrinfo

  commit a8ae7d19
  Author: Daniel P. Berrange <berrange@redhat.com>
  Date:   Thu Oct 21 11:13:05 2010 +0100

    Remove all use of inet_pton and inet_ntop
Reviewed-by: NJán Tomko <jtomko@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

bootstrap.conf

@@ -58,7 +58,6 @@ gettimeofday
 gitlog-to-changelog
 gnumakefile
 ignore-value
-inet_pton
 intprops
 ioctl
 isatty