correct x86_64 snapshot hash for linux

Author: nikomatsakis

src/snapshots.txt

@@ -1,7 +1,7 @@
 S 2012-08-09 1b2d91c
   winnt-i386 52d027feab4342413bda232eaf7c904d0a2494cd
   linux-i386 31d3c1f060e885b7676e60632de1f02f47ed9730
-  linux-x86_64 31d3c1f060e885b7676e60632de1f02f47ed9730
+  linux-x86_64 e8dd42094793c4dede12af4c6bd779328f689eff
   freebsd-x86_64 644da9d954107da5a8fa7566cb1248e95410250d
   macos-i386 f5b22b1524b3b947197c6e826361a426c7327f6f
   macos-x86_64 7cd5e146d837294c270db75dbd2f70d5be8292cf