Introduce a new type, PtrdiffT.  Replace lots of uses of OffT (all those
that are memory offsets) with PtrdiffT;  OffT should only be used for file
sizes and offsets.

Change Off64T from a ULong to a Long, as it should be.  Replace some uses
of ULong in the address space manager with Off64T to match.

Also add a comment explaining the meanings of the basic types like Addr,
OffT, SizeT, etc.

Also fix the prototype for VG_(pread) -- the last arg is an OffT, not an
Int.



git-svn-id: svn://svn.valgrind.org/valgrind/trunk@8959 a5019735-40e9-0310-863c-91ae7b9d1cf9
diff --git a/include/pub_tool_aspacemgr.h b/include/pub_tool_aspacemgr.h
index 6144d27..1186551 100644
--- a/include/pub_tool_aspacemgr.h
+++ b/include/pub_tool_aspacemgr.h
@@ -101,7 +101,7 @@
       /* Associated file (SkFile{C,V} only) */
       ULong   dev;
       ULong   ino;
-      ULong   offset;
+      Off64T  offset;
       UInt    mode;
       Int     fnIdx;    // file name table index, if name is known
       /* Permissions (SkAnon{C,V}, SkFile{C,V} only) */