Compiled and run in x86_64.
Changes:
-Define CK_ATTRIBUTE_FORMAT for GCC >= 2.95.3, to make use of ‘gnu_printf’ format attribute
-Refactor tests to fix signed - unsigned conversions
-Refactor some Check internals to use proper interger types
Signed-off-by: Eduardo Abinader <eduardoabinader@gmail.com>