Ziplist encoding now tested with negative integers as well.
Fix and refactoring of code used to get registers on crash.

This fixes compilation on FreeBSD (and possibly other systems) by
not using ucontext_t at all if HAVE_BACKTRACE is not defined.
Also the ifdefs to get the registers are modified to explicitly test for the
operating system in the first level, and the arch in the second level
of nesting.
A few compiler warnings suppressed.
Fixed a bug in propagation of PUBLISH via the cluster bus.

This bug was spotted by clang on FreeBSD.
Add a 24bit integer to ziplists to save one byte for ints that can
fit in 24 bits (thanks to antirez for catching and solving the two's compliment
bug).

Increment REDIS_RDB_VERSION to 6
ziplist.c: added comments about the new 24 bit encoding.
rdbLoad() should check REDIS_RDB_VERSION instead of hardcoded number.
Added two new encodings to ziplist.c

1) One integer "immediate" encoding that can encode from 0 to 12 in the
encoding byte itself.
2) One 8 bit signed integer encoding that can encode 8 bit signed small
integers in a single byte.

The idea is to exploit all the not used bits we have around in a
backward compatible way.
Spurious debugging printf removed.
redis-check-dump now is RDB version 6 ready.
Explicitly use bash for install_server.sh. Fixes issue #397
Spelling: s/synchrnonization/synchronization
Merge pull request #481 from dtran320/unstable

Spelling: s/synchrnonization/synchronization
Redis test: scripting EVALSHA replication test more reliable.

A new primitive wait_for_condition was introduced in the scripting
engine that makes waiting for events simpler, so that it is simpler to
write tests that are more resistant to timing issues.
Merge remote-tracking branch 'origin/unstable' into unstable
Redis test: More reliable BRPOPLPUSH replication test.

Now it uses the new wait_for_condition testing primitive.
Also wait_for_condition implementation was fixed in this commit to properly
escape the expr command and its argument.
Don't use an alternative stack for SIGSEGV & co.

This commit reverts most of c575766202773c858be0870c20cd495b722927c3, in
order to use back main stack for signal handling.

The main reason is that otherwise it is completely pointless that we do
a lot of efforts to print the stack trace on crash, and the content of
the stack and registers as well. Using an alternate stack broken this
feature completely.
Produce the stack trace in an async safe way.
Re-introduce -g -rdynamic -ggdb when linking, fixing strack traces.

A previous commit removed -g -rdynamic -ggdb as LDFLAGS, not allowing
Redis to produce a stack trace wth symbol names on crash.
This commit fixes the issue.
Set LUA_MASKCOUNT hook more selectively. Fixes issue #480.

An user reported a crash with Redis scripting (see issue #480 on
github), inspection of the kindly provided strack trace showed that
server.lua_caller was probably set to NULL. The stack trace also slowed
that the call to the hook was originating from a point where we just
used to set/get a few global variables in the Lua state.

What was happening is that we did not set the timeout hook selectively
only when the user script was called. Now we set it more selectively,
specifically only in the context of the lua_pcall() call, and make sure
to remove the hook when the call returns. Otherwise the hook can get
called in random contexts every time we do something with the Lua
state.