Getting rid of some compiler warnings

BufferData(...) returns a const char * pointer and we were feeding it
straight into a function that needs a char *. This change forces the
cast from const char * to char *.
Changing signature for List Constructor.
Fixing conflicts

The previous pull request was not merged on time and the underlying code
changed, therefore I need to manually resolve the conflicts.
Adding a second constructor for Buffer.

Buffer *BufferNewFrom(const char 'data, unsigned int length);

It can initialize a buffer from a const char pointer.
Merge pull request #345 from cduclos/master

Datastructure changes: Changed the signature of the list constructor and added a secondary constructor for Buffer.