automake: display whether sleep supports fractional seconds as yes/no. https://lists.gnu.org/archive/html/automake/2024-07/msg00003.html * m4/sanity.m4 (_AM_SLEEP_FRACTIONAL_SECONDS): Set am_cv_sleep_fractional_seconds to yes/no, not true/false, for consistency with other results. Also "quote" this and other $am_cv values. (_AM_FILESYSTEM_TIMESTAMP_RESOLUTION): Test for yes/no. * t/ax/test-defs.in: Set am_cv_sleep_fractional_seconds to 'no', not 'false'.