Return the specification version being assumed by the package.
Equivalent to parse_version(getOption('MP_flex_spec_version')).
spec_version()
spec_ver_eq(version)
spec_ver_gt(version)
spec_ver_lt(version)
spec_ver_btwn(version_left, version_right)string with the version of the spec
(e.g. "0.0.5")
string with the exclusive lower bound of the spec version
string with the exclusive upper bound of the spec version
svlist object with the specification version.
Specification Document: https://canmod.net/misc/flex_specs.
spec_ver_eq, spec_ver_gt, spec_ver_lt, and
spec_ver_btwn return logical values indicating whether or not
the spec_version is equal to, greater than, less than or between
a user-specified version.