Changed every memcmp to SCA equivalent mbedtls_platform_memcmp

This makes physical attacks more difficult.
Selftest memcmp functions were not changed.
diff --git a/library/asn1parse.c b/library/asn1parse.c
index aac253b..806724d 100644
--- a/library/asn1parse.c
+++ b/library/asn1parse.c
@@ -431,7 +431,7 @@
     while( list != NULL )
     {
         if( list->oid.len == len &&
-            memcmp( list->oid.p, oid, len ) == 0 )
+            mbedtls_platform_memcmp( list->oid.p, oid, len ) == 0 )
         {
             break;
         }