enhancement/bugfix1965: all specest functions now give warnings when
there is a mismatch between input and output freqoi/timeoii (not a
warning_once)
bugfix: when freqoi = 'all' and timwin is a scalar, timwin is expanded
enhancement+bugfix: all specest functions now give an appropriate
warning when the requested frequency resolution is unattainable with the
requested padding. Bugfix, I forgot an abs in the checks for differences