Fixed possibly undefined variable warnings by initializing variables to 0.
diff --git a/library/entropy.c b/library/entropy.c
index f8db1a5..ac7e905 100644
--- a/library/entropy.c
+++ b/library/entropy.c
@@ -258,7 +258,7 @@
  */
 static int entropy_gather_internal( mbedtls_entropy_context *ctx )
 {
-    int ret, i, have_one_strong = 0;
+    int ret = 0, i, have_one_strong = 0;
     unsigned char buf[MBEDTLS_ENTROPY_MAX_GATHER];
     size_t olen;