Do not warn about madvise not being implemented. It does not have any real
semantic anyway, and that brings some -Werror FTBFS.

--- a/misc/madvise.c
+++ b/misc/madvise.c
@@ -32,4 +32,4 @@ __madvise (void *addr, size_t len, int a
 libc_hidden_def (__madvise)
 weak_alias (__madvise, madvise)
 
-stub_warning (madvise)
+/* stub_warning (madvise) */
--- a/posix/posix_madvise.c
+++ b/posix/posix_madvise.c
@@ -27,4 +27,4 @@ posix_madvise (__ptr_t addr, size_t len,
 {
   return ENOSYS;
 }
-stub_warning (posix_madvise)
+/* stub_warning (posix_madvise) */