* configure.ac (gcc-warnings): Move -Wall before -Wno-sign-compare.
Otherwise, gcc 4.1.0 (at least) warns about sign comparisons in
__AT_CHECK_PRINTER_AND_DESTRUCTOR in tests/actions.at.
* test/input.at (Torturing the Scanner): #include <stdlib.h> for abort.
* test/regression.at (Diagnostic that expects two alternatives):
Likewise.