Fixed compilation with -Wmissing-prototypes.

src/core/ngx_crypt.c

diff --git a/src/core/ngx_crypt.c b/src/core/ngx_crypt.c
index 9564c36..365f9c8 100644
--- a/src/core/ngx_crypt.c
+++ b/src/core/ngx_crypt.c
@@ -6,6 +6,7 @@
 
 #include <ngx_config.h>
 #include <ngx_core.h>
+#include <ngx_crypt.h>
 #include <ngx_md5.h>
 #if (NGX_HAVE_SHA1)
 #include <ngx_sha1.h>