macOS compatibility

[krlmlr]

Upstream issue: gperftools/gperftools#948.

The necessary patch to gperftools is in upstream master but not yet on Debian: gperftools/gperftools#1187. It will take some time to appear on Ubuntu anyway (where it is optional), and can already be installed on Homebrew (using HEAD) where it is mandatory.

Aiming at implementing compatibility with both versions, driven by the configure script.

[dfalster]

Looks like the patch to gperftools/gperftools#1187 been merged, and is available via gperftools from v2.8

[krlmlr]

Thanks. Would you like to contribute?

[dfalster]

Possibly, likely beyond my skillset. What is needed? I can't commit right now as in the middle of teaching term, but will take a look mid year and see where it's up to.