Add fix from PR44656 to fix sig6 in postfix/smtp when compiled with any type
of DB support (like mysql, postgres, etc).  Also fixes PR43637
Tested by me.
After some discussion with ansible folks, don't replace the interpreter
in modules (the files in ${WRKSRC}/library), as they're treated as
data and not scripts - the right thing to do is to set
"ansible_python_interpreter" in the configuration.

Also, install example files in ${PREFIX}/share/examples/ansible.
Fix libpng fallout.
On NetBSD, link against libexecinfo when backtrace(3) is desired.
Require C++11 when building with Clang. Fix fallout of Boost update due
to MOC's limited C preprocessor. Derive template arguments of make_pair
automatically.
Honor sequence point rules.
Don't use string variables as format strings, especially if they are
from the outside world. Make two clang warnings non-fatal that seem to
be harmless.