Split HAVE_TIME into HAVE_TIME + HAVE_TIME_DATE

First one means we have time() but it may not return the actual wall clock
time, second means it does.
diff --git a/include/mbedtls/check_config.h b/include/mbedtls/check_config.h
index 5f620be..9fb870a 100644
--- a/include/mbedtls/check_config.h
+++ b/include/mbedtls/check_config.h
@@ -44,6 +44,10 @@
 #error "MBEDTLS_DEPRECATED_WARNING only works with GCC and Clang"
 #endif
 
+#if defined(MBEDTLS_HAVE_TIME_DATE) && !defined(MBEDTLS_HAVE_TIME)
+#error "MBEDTLS_HAVE_TIME_DATE without MBEDTLS_HAVE_TIME does not make sense"
+#endif
+
 #if defined(MBEDTLS_AESNI_C) && !defined(MBEDTLS_HAVE_ASM)
 #error "MBEDTLS_AESNI_C defined, but not all prerequisites"
 #endif