Resolver: added missing sanity checking when creating name queries.

Found by Veracode.

src/core/ngx_resolver.c

diff --git a/src/core/ngx_resolver.c b/src/core/ngx_resolver.c
index 2e30471..02c484d 100644
--- a/src/core/ngx_resolver.c
+++ b/src/core/ngx_resolver.c
@@ -1840,7 +1840,7 @@
             len++;
 
         } else {
-            if (len == 0) {
+            if (len == 0 || len > 255) {
                 return NGX_DECLINED;
             }
 
@@ -1851,6 +1851,10 @@
         p--;
     }
 
+    if (len == 0 || len > 255) {
+        return NGX_DECLINED;
+    }
+
     *p = (u_char) len;
 
     return NGX_OK;