From Gerri: TFileMerger silently modifies gDirectory. This has weird consequences, in particular people may have a null gDirectory after using TFileMerger.  This patch saves and restores the current gDirectory.
From Gerri:
TFileMerger silently modifies gDirectory. This has weird consequences,
in particular people may have a null gDirectory after using TFileMerger. 
This patch saves and restores the current gDirectory.


git-svn-id: ecbadac9c76e8cf640a0bca86f6bd796c98521e3@44177 27541ba8-7e3a-0410-8455-c3a389f83636

bbannier/ROOT,bbannier/ROOT,bbannier/ROOT,bbannier/ROOT,bbannier/ROOT,bbannier/ROOT,bbannier/ROOT