Change CLG_(get_debug_info) such that it does not build up an absolute
path name. Instead add a function parameter to hold the directory
name, if one was found. Build up the path name when it is needed.
That will come in handy soonish.
This change has some ripple and a few other functions need to be changed
and now take in an additional parameter for the directory as well.
For clarity, change some function parameter types from
HChar [FILENAME_LEN] to const HChar * if the parameter is an 
input parameter.


git-svn-id: svn://svn.valgrind.org/valgrind/branches/BUF_REMOVAL@14289 a5019735-40e9-0310-863c-91ae7b9d1cf9