This patch reorganises sal.c and adds a small amount of new functionality.

 - Introduce sal_revision to report what revision of the SAL spec is
   supported by the system.
 - Introduce sal_version to report what version of the vendor's SAL
   implementation is present.
 - Introduce SAL_VERSION_CODE to allow for easy comparisons.
 - Print the version at boot, and remove the 'oem=' and 'vendor=' strings.
 - Refactor ia64_sal_init() into several smaller functions.
 - Delete the dead variables 'max' and 'min'.
 - Stop printing the pal_proc and sal_proc entry addresses.
 - Print "None" if there are no SAL platform features.