build: add some modules

snprintf is currently implicitly picked up by getaddrinfo, but we
might as well make it explicit so that mingw doesn't break if
getaddrinfo changes to drop the dependency.

func doesn't matter for gcc compilation, but may help other compilers
cope with our use of __func__.

* bootstrap.conf (gnulib_modules): Add snprintf and func.

bootstrap.conf

@@ -29,6 +29,7 @@ count-one-bits
 crypto/md5
 dirname-lgpl
 fcntl-h
+func
 getaddrinfo
 gethostname
 getpass
@@ -53,6 +54,7 @@ random_r
 sched
 send
 setsockopt
+snprintf
 socket
 stpcpy
 strchrnul