[libmicrohttpd] Build failure with Link-Time Optimization

[Sergey Sudnitsyn]

When LTO is enabled, linking fails complaining about potentially
uninitialized variables;
It's hard to provide a small sample reproducing this, but I hope the patch
can be applied even without it since it's innocent enough (diff against
commit 8bb481f ):

diff --git a/src/microhttpd/connection.c b/src/microhttpd/connection.c
index f9892a55..e5dd1a45 100644
--- a/src/microhttpd/connection.c
+++ b/src/microhttpd/connection.c
@@ -653,7 +653,7 @@ MHD_connection_alloc_memory_ (struct MHD_Connection
*connection,
 {
   struct MHD_Connection *const c = connection; /* a short alias */
   struct MemoryPool *const pool = c->pool; /* a short alias */
- size_t need_to_be_freed; /**< The required amount of additional free
memory */
+ size_t need_to_be_freed = 0; /**< The required amount of additional free
memory */
   void *res;

   res = MHD_pool_try_alloc (pool, size, &need_to_be_freed);
@@ -4468,7 +4468,7 @@ process_request_body (struct MHD_Connection
*connection)
       { /* Need the parse the chunk size line */
         /** The number of found digits in the chunk size number */
         size_t num_dig;
- uint64_t chunk_size;
+ uint64_t chunk_size = 0;
         bool broken;
         bool overflow;