Add -Wconditional-uninitialized to clang strict warnings.

Reviewed-by: Rich Salz <rsalz@openssl.org>

apps/s_client.c

diff --git a/apps/s_client.c b/apps/s_client.c
index f4132c8..5971f8a 100644
--- a/apps/s_client.c
+++ b/apps/s_client.c
@@ -656,7 +656,7 @@
     int prexit = 0;
     int enable_timeouts = 0, sdebug = 0, peerlen = sizeof peer;
     int reconnect = 0, verify = SSL_VERIFY_NONE, vpmtouched = 0;
-    int ret = 1, in_init = 1, i, nbio_test = 0, s, k, width, state = 0;
+    int ret = 1, in_init = 1, i, nbio_test = 0, s = -1, k, width, state = 0;
     int sbuf_len, sbuf_off, socket_type = SOCK_STREAM, cmdletters = 1;
     int starttls_proto = PROTO_OFF, crl_format = FORMAT_PEM, crl_download = 0;
     int write_tty, read_tty, write_ssl, read_ssl, tty_on, ssl_pending;