By Bertrand: read new rootmap format.

Reading the new format of rootmap files should be completely backward compatible (all roottests are successful).
The new format looks like the following example, as described in ROOT-5510:

{ decls }
namespace A { template <typename T, int I, typename TAG, typename S = T, int J = I> class Template; }

[MyLib libTree libHist libMatrix]
class A::Template<int, 0, TagClassWithoutDefinition, int ,0>
class A::Template<int, 1, TagClassWithoutDefinition, int ,1>

[MyOtherLib libHist libMatrix]
class MyClass;
namespace TMath;

I also had to modify rootcling.cxx, to make all roottest successfully pass, but Danilo, feel free to review these changes (i.e. namespaces are missing...)