examples: fix compile warnings

Fixes the following two warnings:

    examples/client.c:292:0: error: macro "MAX_OUTLEN" is not used [-Werror=unused-macros]
    examples/tiny-nghttpd.c:298:13: error: function declaration isn’t a prototype [-Werror=strict-prototypes]

Caught using cmake as the autoconf check fails due to unused macros
(HAVE_xxx in conftest.c) and a main function without parameters
respectively.

examples/client.c

@@ -289,8 +289,6 @@ static int on_stream_close_callback(nghttp2_session *session, int32_t stream_id,
   return 0;
 }
 
-#define MAX_OUTLEN 4096
-
 /*
  * The implementation of nghttp2_on_data_chunk_recv_callback type. We
  * use this function to print the received response body.

examples/tiny-nghttpd.c

@@ -295,7 +295,7 @@ static size_t http_date(char *buf, time_t t) {
 static char date[29];
 static size_t datelen;
 
-static void update_date() { datelen = http_date(date, time(NULL)); }
+static void update_date(void) { datelen = http_date(date, time(NULL)); }
 
 static size_t utos(char *buf, size_t len, uint64_t n) {
   size_t nwrite = 0;