Make scansys preserve hand-written annotations on --recheck.

This required a surprisingly large overhaul.  As a side effect,
--recheck will now tell you what, if anything, changed.
Regenerate Debian-unstable inventories with new scansys.

No change in glibc2.17-gcc47, as expected.

Clang 3.0 has been replaced by 3.2, which brings a few new headers.
It appears that 3.0 was erroneously picking up headers that belonged to
GCC, so drop the glibc2.13-clang30 inventory outright.
Sort :ccenv lines on windows-vc* inventories.