fix parallel compilation for the unlikely case of identical time stamps

Since version 24.3 Emacs supports pico second precision in time
stamps and Emacs on ext4 seems to have a time precision of 5
milliseconds for file time stamps. It is therefor quite unlikely
that a source and an object file have the same time stamp. This
patch fixes parallel compilation for these corner cases and adds
a few hundred test cases to test all combinations where some
files have identical time stamps. On Emacs older than 24.3 or on
file systems with a low precision (eg. ext3) this patch can cause
additional compilations.

0 files changed, 0 insertions, 0 deletions