seq: revert Solaris 8 work-around that caused x86 regression

seq: revert Solaris 8 work-around that caused x86 regression

* src/seq.c: Don't include <math.h>, <float.h>.
(abs_rel_diff): Remove.
(print_numbers): Test for equality, not for an epsilonish value.
This reverts 4827dd27b0c655a685947aaa01426a5ecba179f3, aka
v6.10-185-g4827dd2, which broke 'seq' on the x86; for example, it
causes "seq 9223372036854775807 9223372036854775808" to incorrectly
output 3 numbers instead of 2.  It's better to punish obsolescent
hosts that have incorrectly-working floating-point than to punish
correctly-working hosts.
* tests/misc/seq: Use 0.9000000000000, rather than
0.90000000000000000000, to avoid tickling a bug in Solaris 8 strtold,
which converts "0.9" and "0.9000000000000" correctly, but incorrectly
converts "0.90000000000000000000" to a smaller value.