bug#11825: 24.1.50; float-time no longer accepts negative time values

[Paul Eggert]

On 07/06/2012 11:57 PM, Eli Zaretskii wrote:
> Yes, the type used by DJGPP for time_t is unsigned.

OK, thanks, but in that case I don't see how
the use of EMACS_TIME_SIGN in src/msdos.c can
be correct.  On hosts where time_t is unsigned,
EMACS_TIME_SIGN can never be negative.  That's why
I got rid of all uses of EMACS_TIME_SIGN elsewhere,
replacing subtract-and-then-compare-to-zero with
plain compare.  If time_t can be unsigned in msdos.c,
then msdos.c sys_select can be fixed by using
plain compare rather than subtract-and-then-compare-to-zero.
This will allow us to simplify Emacs further by removing
EMACS_TIME_SIGN entirely.