C++11 compatibility for tuples

With C++11 'tuple' also exist in 'std'. For the moment the 'tuple' from
'boost::tuples' should still be used, so explicetly write the namespace at
each usage.
C++11 compatibility for explicit template specialization

Explicitly give the namespace 'rpwa' for the template specializations of
'pwaLikelihood'.
C++11 compatibility for isnan

Explicitely specify the namespace 'std' for 'isnan'.
C++11 compatibility comparing two ostream

'std::ostream' no longer has an implicit conversion to a 'void*'. With
that gone two 'std::ostream' can no longer be compared for equality
directly. The safest way seems to compare the pointers to the underlying
buffers.
C++11 compatibility avoiding rvalue references

Workaround to convince clang not to consider the return value of the
override as an rvalue reference. Otherwise the assignment statement would
have been ambigious.
Check for C++11 compatible compiler

Check whether the compiler understands the '-std=c++11' option, and use
it if possible to enable C++11 (required for ROOT 6).