From Brian:
For CMS backward compatibility, allow SetCacheRead to disconnect the cache from being the current cache, but keep the file attached to the cache.

git-svn-id: http://root.cern.ch/svn/root/branches/v5-34-00-patches@45321 27541ba8-7e3a-0410-8455-c3a389f83636
(cherry picked from v5-34-00-patches commit eac731d2b12532ba0d2cd1986882bc0f82a1b8c4)
From Brian:
For CMS backward compatibility, allow SetCacheRead to disconnect the cache from being the current cache, but keep the file attached to the cache.

git-svn-id: http://root.cern.ch/svn/root/branches/v5-34-00-patches@45322 27541ba8-7e3a-0410-8455-c3a389f83636
(cherry picked from v5-34-00-patches commit c35d989727faa88c2103533e3ed4007919fd0d10)

Conflicts:
	tree/tree/inc/TTreeCache.h
Compile RuntimeException.o with -fexception
White space change (to force recompilation)