Core: fix compiler warnings

Signed-off-by: Eduardo Silva <edsiper@gmail.com>
Virtual Host: File Descriptor Table (FDT).

The File Descriptor Table (FDT) aims to provide a mechanism to share
open file descriptors at Virtual Host level with the goal of to reduce the
number of open file descriptors and reduce the calls to open(2) and close(2).

The FDT is implemented in the following way:

 - For each worker thread, maintain a list matching the global Virtual Host
   list and for each entry create a Hash Table (HT) of 64 entries, and each
   HT entry maintain a sub-array of 8 chains.

 - When a request for a static file arrives, use the new Virtual Host open/close
   wrappers, from the given parsed and processed URI generate a hash value and
   try to see if it exists in the HT, if it don't exist, just open the file
   directly and register the data into the chain for a possible future reuse.

   If the hash exists in some HT/Chain, obtain the opened file descriptor and
   increment the readers counter.

 - When the Monkey core do not longer needs the file descriptor, instruct the
   Virtual Host 'close' wrapper to perform the cleanup. If the resource/hash
   exists in the HT/Chain, decrement the readers counter, if counter reach
   zero, just perform an explicit close(2) as nobody is using it, if readers
   is greater than zero just return as the file descriptor is in use.

   If the resource do not exists in the HT, do a direct close(2).

The good thing of this implementation is that exists at worker level, so there
is no race conditions and is lock-free. Also collisions are reduced to zero
using HashTable Chaining. The hashing algorithm in use MurmurHash 2.

This implementation reduce the overhead under high concurrency sharing the file
descriptor resources and making it more scalable.

Signed-off-by: Eduardo Silva <edsiper@gmail.com>
Virtual Host: reduce hashed string on FDT.

Signed-off-by: Eduardo Silva <edsiper@gmail.com>
Scheduler: optimize access to thread specific data with __thread

Signed-off-by: Eduardo Silva <edsiper@gmail.com>