[cache] Deduplicate the code to get the top node by a hash.

There are several duplicated codes getting the top node
from a cache by a given hash, like:

    idx = hash & cache->mask;
    if ( idx < cache->p )
      idx = hash & ( cache->mask * 2 + 1 );
    pnode = cache->buckets + idx;

To deduplicate them, a cpp-macro to do same work
FTC_NODE__TOP_FOR_HASH( cache, hash ) is introduced.
For non-inlined config, non-ftc_get_top_node_for_hash() is
also introduced.

* src/cache/ftccache.h (FTC_NODE__TOP_FOR_HASH): Declare
and implement inlined version.
(FTC_CACHE_LOOKUP_CMP): Use FTC_NODE__TOP_FOR_HASH().
* src/cache/ftccache.c (ftc_get_top_node_for_hash): Non-
inlined version.
(ftc_node_hash_unlink): Use FTC_NODE__TOP_FOR_HASH().
(ftc_node_hash_link): Ditto.
(FTC_Cache_Lookup): Ditto.
3 files changed