[patch] Enable lightweight checks with _GLIBCXX_ASSERTIONS.

[Florian Weimer]

* Jonathan Wakely:

> This patch adds the "debug mode lite" we've been talking about, by
> changing __glibcxx_assert to be activated by _GLIBCXX_ASSERTIONS
> instead of _GLIBCXX_DEBUG (and making the latter imply the former).

Interesting.  Is this mode ABI-compatible with the default mode?
Should _FORTIFY_SOURCE imply _GLIBCXX_ASSERTIONS?