Added member function Attribute::getInMemDataSize() to simplify
getting the attribute's data size in memory. Used this new function
in Attribute::read to get the fixed-len string attribute data.
Added tests to tattr.cpp.
Platforms tested:
Linux/32 2.6 (jam)
FreeBSD/64 6.3 (liberty)
SunOS 5.10 (linew)
91e9a5d5c8