Convert C struct definitions into Python classes with methods for
serializing/deserializing. The usage is very simple: create a class
subclassing cstruct.CStruct and add a C struct definition as a
string in the struct field. The C struct definition is parsed at
runtime and the struct format string is generated. The class offers
the method "unpack" for deserializing a string of bytes into a
Python object and the method "pack" for serializing the values into
a string.