deflate: add new deflate_quick strategy for level 1

The deflate_quick strategy is designed to provide maximum
deflate performance.

deflate_quick achieves this through:
    - only checking the first hash match
    - using a small inline SSE4.2-optimized longest_match
    - forcing a window size of 8K, and using a precomputed dist/len
      table
    - forcing the static Huffman tree and emitting codes immediately
      instead of tallying

This patch changes the scope of flush_pending, bi_windup, and
static_ltree to ZLIB_INTERNAL and moves END_BLOCK, send_code,
put_short, and send_bits to deflate.h.

Updates the configure script to enable by default for x86. On systems
without SSE4.2, fallback is to deflate_fast strategy.

Fixes #6
deflate: add new deflate_medium strategy

From: Arjan van de Ven <arjan@linux.intel.com>

As the name suggests, the deflate_medium deflate strategy is designed
to provide an intermediate strategy between deflate_fast and deflate_slow.
After finding two adjacent matches, deflate_medium scans left from
the second match in order to determine whether a better match can be
formed.

Fixes #2
deflate: avoid use of uninitialized variable

(Note emit_match() doesn't currently use the value at all.)

Fixes #4
Include wmmintrin.h in configure test and crc_folding.c aid clang compilation.
Add forward declarations for fill_window_sse and flush_pending to deflate_quick.c.
Add crc_ forward declarations to deflate and add read_buf fwd dcl to fill_window_sse.