fix 'make dist'.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@1977 a5019735-40e9-0310-863c-91ae7b9d1cf9
diff --git a/coregrind/Makefile.am b/coregrind/Makefile.am
index 7546e63..c86c6a3 100644
--- a/coregrind/Makefile.am
+++ b/coregrind/Makefile.am
@@ -88,6 +88,7 @@
         vg_include.h            \
         vg_constants.h          \
 	vg_symtab2.h		\
+        vg_unistd.h             \
 	vg_symtypes.h		\
 	vg_unsafe.h