[Toybox] [PATCH] man: support MANPATH.

[makepost]

On Mon, Apr 29, 2019 at 04:33:07PM -0700, enh via Toybox wrote:
+  if (!TT.M) TT.M = getenv("MANPATH");

Breaks unfortunately, distros e.g. gentoo are prefixing the main path in
the variable with colon divided binutils and gcc dirs, apparently for
allowing to install multiple versions and architectures on same system.
I can rework tryfile and FLAG(k) from yesterday's patch to walk every
directory from this variable, would that be viable?