Update README.md

Author: mcarbonneaux

README.md

@@ -21,6 +21,8 @@ You must have compiled and installed:
 
 - [libmemcache](https://github.com/richp10/libmemcache-1.4.0.rc2-patched) the C client API needed to compile the Apache Module.
 
+Attention: Don't mix up libmemcache and libmemcached!
+
 # How to build
 
 ```