Update jemalloc to 4.2.1 (#1839)

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

@@ -31,6 +31,8 @@ class Jemalloc(Package):
     homepage = "http://www.canonware.com/jemalloc/"
     url      = "https://github.com/jemalloc/jemalloc/releases/download/4.0.4/jemalloc-4.0.4.tar.bz2"
 
+    version('4.2.1', '094b0a7b8c77c464d0dc8f0643fd3901')
+    version('4.2.0', 'e6b5d5a1ea93a04207528d274efdd144')
     version('4.1.0', 'c4e53c947905a533d5899e5cc3da1f94')
     version('4.0.4', '687c5cc53b9a7ab711ccd680351ff988')