- use Clang instead of Gcc for Darwin since this is its system
compiler. The user can force use of Gcc by using Gcc92 etc.
- make etc/cshrc sed check more robust.
- replace tcsh (${%var}) syntax with ("${var}" != "")
[Fixes and ideas from Alexey Matveichev]
CONFIG: do not source the gperftools environment by default
- this is now an used feature, but can be re-enabled by advanced users
if required.