The shared and weak pointers are now included via ACGL.hh, this way there is one
one central place to replace the pointers if needed (C++11, TR1, boost, own variant).
For this, they are placed in a ptr namespace so std:: (C++11) and str::tr1:: (C++98)
variants as well as boost and own implementations can all get redirected.
C++11 detection added and correct non-tr1 header include added (should make VS2010
porting easier).