color/roundtrips test fails on Debian i386, probably due to i387 extended precision

not ok /color/roundtrips - ERROR:../../../testsuite/gtk/colorutils.c:43:test_roundtrips: assertion failed (r == tests[i].r (+/- FLT_EPSILON)): (1.1920929e-07 == 0)

The current baseline for Debian's i386 architecture is i686 minus one instruction, so it does not have MMX, SSE or -mfpmath=sse, and small differences like this are probably to do with i387 floating-point excess precision.

I'm testing a patch that uses 1e-6 on i386 and FLT_EPSILON everywhere else.