Initial commit that introduces UDF (user defined flags).

Memcached.txt specifies that flags are a 16-bit integer. Since the library uses
internally 8 bits to store type, compression and serialization, this leaves us
8 bytes left to store user data. So basically added the udf_flags parameter to
all relevant functions to store and retrieve them.
Was a bit too greedy with all the errors
updated memcached documentation
Final fixes and tests, cleanup
Merge remote-tracking branch 'parent/master' into feature-udf
Test flags
Test memcached version when using flags
Dont break old libmemcached
This should return a value
Remove version check //cc #92
Merge branch 'master' of github.com:php-memcached-dev/php-memcached into testing-flags
Merging from poison/feature-udf. Changed flags for parse parameters to long. //cc #92
Missing casts
More testing of user flags
Test user flags with compression
Fixes comments by @poison
Fixes error with mixing semicolon
Merge pull request #97 from mkoppanen/testing-flags

Testing flags