Fix types of copy/move constructors in interval.h
Add missing initialization of numeric_traits<mpfp>::rnd
Add double/mpfp interval tests
Fix compile-error by adding "defined" to interval_def.h
Disable thread-related tests on OSX due to the bug on gcc-4.8.1
Fix cygwin problem.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Remove unnecessary '--' in status messages

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>