#25 a flaw in metadata merge code

[Vlad Roubtsov]

The "has full debug info" flag is not reset correctly
in the following scenario:

(1) class X is added to metadata without full debug info
(2) class X is later added to the same metadata file
again, with full debug info.

The symptoms are that the report tool incorrectly
report that there classes with incomplete debug info,
but a listing of sample such classes is empty.