The chroots in which we often build Open vSwitch don't have /proc and
thus cannot support /dev/stdin, because on Linux that is a symlink to
/proc/self/fd/0. So avoid using /dev/stdin in the testsuite.
The test for whether a real number was outside the valid range was
imprecise and failed at the edge of the real range. This commit changes
the code to use the C library's strtod(), which presumably does better.
The previous code checked only that JSON objects have members with the
same names. This commit makes json_equal() also check that like-named
members have the same values.
