MEMCACHED_CALLBACK_PREFIX_KEY renaming breaks build on older libmemcached versions

[ketralnis]

At some point MEMCACHED_CALLBACK_PREFIX_KEY was renamed to MEMCACHED_CALLBACK_NAMESPACE, but libmemcached in 0.44 won't compile with that name. Should this be named conditionally? Or maybe the renaming can be smoothed on the pylibmc side for consistency

~/src/pylibmc (master)$ python ./setup.py build
running build
running build_py
running build_ext
building '_pylibmc' extension
gcc -fno-strict-aliasing -arch x86_64 -g -Os -pipe -no-cpp-precomp -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -DUSE_ZLIB -I/usr/local/include/python2.7 -c src/_pylibmcmodule.c -o build/temp.macosx-10.4-x86_64-2.7/src/_pylibmcmodule.o -fno-strict-aliasing
In file included from src/_pylibmcmodule.c:34:
src/_pylibmcmodule.h:227: error: ‘MEMCACHED_CALLBACK_NAMESPACE’ undeclared here (not in a function)
src/_pylibmcmodule.c: In function ‘PylibMC_Client_touch’:
src/_pylibmcmodule.c:1074: warning: implicit declaration of function ‘memcached_touch’
error: command 'gcc' failed with exit status 1

[lericson]

Right, I'm partly inclined to bump the requirements to libmemcached 1.0.0 instead. I will merge a fix if you make one. Do you actually still use 0.44?

[ketralnis]

I folded this into the PR I did for compress_level, but it can be cherry-picked off

[ketralnis]

I do actually still use 0.44, yeah :(

[lericson]

How do you get the 0.44 source code, at some museum? ;-) Joking aside, I'm swamped at the moment so will merge later.

[spladug]

FYI, 0.44 is the version of libmemcached in the current Ubuntu Long Term Support release.