add PMDK 1.6

- also remove superflous ncurses dependency for PMDK 1.5

var/spack/repos/builtin/packages/pmdk/package.py

@@ -18,10 +18,9 @@ class Pmdk(Package):
     git      = "https://github.com/pmem/pmdk.git"
 
     version('develop', branch='master')
+    version('1.6',     sha256='3b99e6c30709326a94d2e73a9247a8dfb58d0a394c5b7714e5c3d8a3ad2e2e9f')
     version('1.5',     sha256='6b069d7207febeb62440e89245e8b18fcdf40b6170d2ec2ef33c252ed16db2d4')
 
-    depends_on('ncurses', when='@1.5:')
-
     # documentation requires doxygen and a bunch of other dependencies
     patch('0001-make-doc-building-explicit.patch')