Indicate that the truncation from size_t to int is deliberate

MPI sizes do fit in int. Let MSVC know this conversion is deliberate.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/library/debug.c b/library/debug.c
index c8ef9b5..a9820bf 100644
--- a/library/debug.c
+++ b/library/debug.c
@@ -246,7 +246,7 @@
     else
     {
         int n;
-        for( n = ( bitlen - 1 ) / 8; n >= 0; n-- )
+        for( n = (int) ( bitlen - 1 ) / 8; n >= 0; n-- )
         {
             size_t limb_offset = n / sizeof( mbedtls_mpi_uint );
             size_t offset_in_limb = n % sizeof( mbedtls_mpi_uint );