There can be multiple [heap] consecutively in proc/<pid>/maps,
and there's no room between them.
Don't use a hole after the first [heap] is there's another [heap]
immediately after it.
This code would fail to find the last [heap] if there were multiple
[heap] interleaved with non-heap VMA, but our kind "after heap"
wouldn't be meaningful anymore anyway.
Signed-off-by: Brice Goglin <Brice.Goglin@inria.fr>
8f6afbb641