interesting mainline failures, 1/2

[Loren James Rittle]

Given Mark's intention to cut a branch ASAP once various PRs are
resolved motivated me to look at outstanding failures...

FAIL: 23_containers/bitset/invalidation/1.cc (test for excess errors)
[...]1.cc:24: error: use of `bitset' is ambiguous
[...]include/debug/bitset:42: error:   first declared as `template<unsigned
 int _Nb> class __gnu_debug_def::bitset' here
[...]include/bitset:604: error:   also declared as `template<unsigned int _Nb>
  class __gnu_norm::bitset' here

[20 more 'invalidation' tests, each failing in a similar manner.]

Known issue?  Or, only on my *freebsd4 system (not seen on ref5)?  I
don't see this on any other platform's test results.

There is a 'using namespace std;' inside namespace __gnu_debug . Is
that correct?  Seems to introduce the ambiguous definition?  Then
again, I admit I have no idea what this '__attribute__ ((strong))' is
suppose to do to ambiguity calculations (that aspect is not documented
in gcc/doc/extend.texi from my reading).