Add missing forward decl and includes in TString.h
Add missing forward decl and includes in TString.h

All these declarations comming from TMathBase.h,
which may (or will) be changed in the future

olifre/root,root-mirror/root,karies/root,karies/root,olifre/root,karies/root,karies/root,root-mirror/root,root-mirror/root,karies/root,karies/root,olifre/root,karies/root,olifre/root,karies/root,karies/root,olifre/root,olifre/root,olifre/root,root-mirror/root,root-mirror/root,root-mirror/root,olifre/root,olifre/root,karies/root,root-mirror/root,olifre/root,karies/root,root-mirror/root,root-mirror/root,olifre/root,root-mirror/root,root-mirror/root