Fixed most of the warnings in dcmdata.

Compiled with extensive warning options except -Wtraditional and corrected
most of the problems. Most of the remaining warnings in dcmdata are caused by
files included from ofstd and will be resolved in a different commit.
Fixed a mistake in CHANGES.361.
Added readPatientData() and readStudyData().

Added methods for reading data from Patient Module and General Study Module.
This facilitates associating SR documents with an existing patient or study.
Updated outdated comments on "log stream".