fix part of Uses section in Porter's Handbook

[linimon]

Summary

The text describing compiler.mk is too hard to read.

In addition, it misses describing c++11-lang, and 'env' (the default). For these, copy the descriptions from Mk/Uses/compiler.mk.

[mat]

I would rather all the USES have the same way to display their arguments, so I would rather you keep the way it was written before, or change all of them :-)

[linimon]

Incorporate feedback.

[mat]

books/porters-handbook/uses/chapter.xml

281 ↗

(On Diff #43291)

Please, add a space after the :. I think it is important to keep the (none), even if it means env, because there can be no arguments.

[linimon]

Updated per request