Fix misuse of signed ints in the HAVEGE module

Update havege.h to the new version in the crypto module.

This is technically an API break, since the type mbedtls_havege_state
is exposed in a public header. However normal applications should not
be affected.

There is no ABI break on platforms where uint32_t and int are treated
identically, which is virtually all of them.

Fix #2598
diff --git a/include/mbedtls/havege.h b/include/mbedtls/havege.h
index 4c1c860..749257a 100644
--- a/include/mbedtls/havege.h
+++ b/include/mbedtls/havege.h
@@ -31,6 +31,7 @@
 #endif
 
 #include <stddef.h>
+#include <stdint.h>
 
 #define MBEDTLS_HAVEGE_COLLECT_SIZE 1024
 
@@ -43,9 +44,9 @@
  */
 typedef struct mbedtls_havege_state
 {
-    int PT1, PT2, offset[2];
-    int pool[MBEDTLS_HAVEGE_COLLECT_SIZE];
-    int WALK[8192];
+    uint32_t PT1, PT2, offset[2];
+    uint32_t pool[MBEDTLS_HAVEGE_COLLECT_SIZE];
+    uint32_t WALK[8192];
 }
 mbedtls_havege_state;