Add configuration file in md.h

include `*config.h*` in md.h as MACROS in the header file get ignored.
Fix for #1001.
diff --git a/ChangeLog b/ChangeLog
index e8d1da5..a58975e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -41,6 +41,8 @@
    * Fix a potential integer overflow in the version verification for DER
      encoded X509 certificates. The overflow would enable maliciously
      constructed certificates to bypass the certificate verification check.
+   * Include configuration file in md.h, to fix compilation warnings.
+     Reported by aaronmdjones in #1001
 
 Changes
    * Added config.h option MBEDTLS_NO_UDBL_DIVISION, to prevent the use of