Merge r14202 from the BUF_REMOVAL branch to trunk.
This patch changes the interface and behaviour of VG_(demangle) and
VG_(maybe_Z_demangle). Instead of copying the demangled name into a
fixed sized buffer that is passed in from the caller (HChar *buf, Int n_buf),
the demangling functions will now return a pointer to the full-length
demangled name (HChar **result). It is the caller's responsiblilty to
make a copy if needed. 

This change in function parameters ripples upward
- first: to get_sym_name
- then to the convenience wrappers
  - VG_(get_fnname)
  - VG_(get_fnname_w_offset)
  - VG_(get_fnname_if_entry)
  - VG_(get_fnname_raw)
  - VG_(get_fnname_no_cxx_demangle)
  - VG_(get_datasym_and_offset)

The changes in foComplete then forces the arguments of
  - VG_(get_objname) to be changed as well

There are some issues regarding the ownership and persistence of
character strings to consider.
In general, the returned character string is owned by "somebody else"
which means the caller must not free it. Also, the caller must not 
modify the returned string as it possibly points to read only memory.
Additionally, the returned string is not necessarily persistent. Here are
the scenarios:
- the returned string is a demangled function name in which case the
  memory holding the string will be freed when the demangler is called again.
- the returned string hangs off of a DebugInfo structure in which case
  it will be freed when the DebugInfo is discarded
- the returned string hangs off of a segment in the address space manager
  in which case it may be overwritten when the segment is merged with
  another segment
So the rule of thunb here is: if in doubt strdup the string.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14664 a5019735-40e9-0310-863c-91ae7b9d1cf9