Renumber flags version numbers in 'filterConfigureFlags'.
Previously, the code was inconsistent on whether or not flags_x_y_z indicated that these flags could be used up to version x.y.z, or should be used prior to x.y.z. This commit picks the LATTER and renames everything consistently this way. The bonus is that now the names match up with the conditionals. Yay. Signed-off-by: Edward Z. Yang <email@example.com>