compiler-gcc4.h: correct verion check for __compiletime_error

__attribute__((error(msg))) was introduced in gcc 4.3 (not 4.4) and as I
was unable to find any gcc bugs pertaining to it, I'm presuming that it
has functioned as advertised since 4.3.0.

Signed-off-by: Daniel Santos <daniel.santos@pobox.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: David Rientjes <rientjes@google.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>