* pam_krb5.spec: bump version to 2.1.20
    * src/options.c,src/minikafs.c,src/afs5log.c: merge Jan Iven's changes
    	to add a "nullafs" option, so that when we're guessing the principal
    	name for an AFS service we'll try the no-instance version first
    	(#249558)
    * src/minikafs.c: if we're going to guess the realm name because
    	the whereis pioctl failed, guess the far-more-likely-to-be-correct
    	upper cased version of the cell's name than the cell's name.
    (cherry picked from commit 0ab1118dc5f96693f63c554b13ae51df40ad0f86)