Collection of remaining powerpc64le-linux-gnu issues

[redstar]

The following test cases from dmd testsuite still fail on powerpc64le-linux-gnu:

runnable/test12.d: assertion failure in line 490
runnable/cppa.d: undefined reference
runnable/test4.d: assertion failure in line 259
runnable/test5854.d: assertion failure in line 32
runnable/template1.d: assertion failure in line 1462
runnable/testsafe.d: ? (return code 1)
runnable/externmangle.d: undefined reference to `test35(long double)'
runnable/closure.d: assertion failure in line 720
runnable/cabi1.d: assertion failure in line 26

In druntime/Phobos there are the following failures. At first glance all seem to be related to math precision:

core.math
std.typecons
std.complex
std.stream
std.format
std.math
std.conv
std.internal.math.gammafunction
std.internal.math.errorfunction

[redstar]

The undefined reference errors are interesting. They fall in 2 categories:

Compiler dependent: void foo14a(std::basic_string<char> *p) is mangled as _Z6foo14aPSs with gcc 4.9.2 (and ldc2) and as _Z6foo14aPNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE with gcc 5.2.1. Does this happen on other Linux platforms, too?

Math related: long double testld(long double ld) is mangled as _Z6foo14aPSs by ldc2 (because we treat double == long double) and as _Z6foo14aPSs by gcc 5.2.1.