Fix the build without check_config.h (inclusion of limits.h)

Including `mbedtls/check_config.h` from `mbedtls/config.h` is optional. If
done, `limits.h` gets included. If not done, we were missing the inclusion
of `limits.h` in several source files. Fix this and add a test build that
doesn't include `mbedtls/check_config.h`.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/library/ssl_msg.c b/library/ssl_msg.c
index 5e85679..1613a1e 100644
--- a/library/ssl_msg.c
+++ b/library/ssl_msg.c
@@ -29,6 +29,7 @@
 #include "constant_time_internal.h"
 #include "mbedtls/constant_time.h"
 
+#include <limits.h>
 #include <string.h>
 
 #if defined(MBEDTLS_USE_PSA_CRYPTO)