Fix several problems with raw compression:

* when shuffling entries around, ranges can overlap (found by valgrind).
  Use memmove rather than memcpy.

* use the allocation size to figure out which keys can't be split: with
  512 byte leaf pages, the first offset was always near 1KB so compression
  almost always failed.

* provide a way for raw compression to indicate that compression failed so
  that WiredTiger immediately falls back to compressing the entire page,
  rather than calling raw compression again with more records.
Fix some zlib-specific issues:
* always try to compress at least one item (WiredTiger makes the first "row" artificially large);
* loop on all calls since the zlib API allows calls to work incrementally
* reserve more bytes to finish up the last block, and fall back to "normal" compression if the reserved space is insufficient.
typo
Add a comment so the memmove doesn't get reverted to memcpy for
performance reasons.
We use 0/zero inconsistently in the documentation, fix one place so we
don't in adjacent paragraphs, talking about the same variables.
Rewrite the retry/no-retry paragraphs to echo each other "if no rows
could be compressed" isn't the same as "don't try again".
Zlib compression does "raw" compression in all cases, rename the "raw"
configuration to bzip-raw.

Leave bzip raw in place, it deliberately tries to hit some of the edge
cases around raw compression, which can't hurt.
Remove the automake shared library magic around loading the bzip2 compressor
in raw-test mode, it's a lot simpler to load two compressors, the normal one
and a raw-test version.
Merge branch 'develop' into zlib-fixes
Make the first block sent to compress_raw fill a disk allocation block.  If it doesn't compress, there is now a way for the callback to indicate that.
Only retry compress_raw if it returns EAGAIN.  Otherwise, if no rows were compressed, assume that compression failed and fall back to standard compression.
Merge pull request #865 from wiredtiger/zlib-fixes

zlib fixes, including changes to the raw compression interface so that the callback can give up gracefully when compression doesn't work.