biology/openbabel seems to require lower gcc version

[Mayuresh <mayuresh%acm.org@localhost>]

On NetBSD 8.0_RC1 with default gcc 5.5.0 openbable shows compilation
errors of the kind:

/usr/pkgsrc/biology/openbabel/work/openbabel-2.3.2/include/openbabel/shared_ptr.h:33:17:
error: 'std::tr1' has not been declared
      using std::tr1::shared_ptr;

Tried setting the standard to c++11 (instead of c++03 set in the
Makefile). With that, the above error goes away, but a newer one appears
like:

/usr/include/g++/bits/stl_pair.h:276:5: note:   template argument
deduction/substitution failed:
/usr/pkgsrc/biology/openbabel/work/openbabel-2.3.2/src/ops/sort.cpp:147:68:
note:   cannot convert 'iter.__
gnu_cxx::__normal_iterator<_Iterator,
_Container>::operator*<OpenBabel::OBBase**, std::vector<OpenBabel::OB
Base*> >()' (type 'OpenBabel::OBBase*') to type 'OpenBabel::OBBase*&&'
       valvec.push_back(std::make_pair<OBBase*,std::string>(*iter, s));

On Linux with gcc 4.9.2 it is building fine.

Is there a way I can ask pkgsrc to use older gcc version than the default
one? I tried setting variables mentioned on this page, but nothing worked:
compiler always defaulted to 5.5.0

https://wiki.netbsd.org/pkgsrc/gcc/

Please advise.

Mayuresh