Happening when using clang and templated operators, clang cannot decide
between the operator provided by ReusableStringStream and the one provided
by the value value as both are templates. This is easily solved by calling
the operator<< through the member syntax.

Fixes #1285

This was removed in 64be2ad, to fix OS X approval tests. At the time
I couldn't investigate because I didn't have access to OS X, but this
fixed it (and since we don't have MinGW in CI, the breakage went
unnoticed).

As it turns out, piece-wise compilation of the Compact
reporter had broken OS X detection for a long time, and fixing it
was what broke the approvals. After the approval scripts were
changed to compensate, this change passes approval tests and fixes

Until now, the stack size for POSIX signal handling was determined by
the implementation defined limit `STKSZ`, which in some cases turned out
to be insufficient, leading to stack overflow inside the signal handler.
The new size, which was determined experimentally, is the larger of 32kb
or `MINSTKSZ`.

Fixes #1225

Related to #1024

This should align more closely with the intended semantics, where
types without `StringMaker` specialization or `operator<<` overload
are passed down to the user defined fallback stringifier.

Related to #1024