[PATCH] Improve -Wmaybe-uninitialized documentation

[Jonathan Wakely <jwakely at redhat dot com>]

The docs for -Wmaybe-uninitialized have some issues:

- That first sentence is looooooong.
- Apparently some C++ programmers think "automatic variable" means one
 declared with C++11 `auto`, rather than simply a local variable.
- The sentence about only warning when optimizing is stuck in between
 two chunks talking about longjmp, which could be inferred to mean
 only the setjmp/longjmp part of the warning depends on optimization.

This attempts to make it easier to parse and understand.

OK for trunk?

Attachment: patch.txt
Description: Text document