Get the version in the header of LIBRARY.
LIBRARY is either a symbol denoting a named feature, or a library
name as string.
If SHOW is non-nil, show the version in the minibuffer.
Return the version from the header of LIBRARY as list. Signal an
error if the LIBRARY was not found or had no proper header.
See Info node `(elisp)Library Headers' for more information
about library headers. (fn LIBRARY &optional SHOW)