kludge to bypass inner valgrind mmap failing due to not observed outer mmap

kludge to bypass inner valgrind mmap failing due to not observed outer mmap

Some tests are failing in an "outer/inner" setup with an "out of memory"
situation reported by the inner (e.g. memcheck/tests/err_disable4.vgtest).

Looks like this is because the inner valgrind aspacemgr believes
a segment is free and can be used, but segment is in fact used by the outer.
This can happen as the inner cannot observe the outer mmap, and so
inner aspacemgr can be out of sync with the kernel and the outer.

This kludge bypasses the problem: if the fixed mmap fails in the inner,
the inner retries without the fixed.
This is a kludge as the proper solution would be to have a correct
state of aspacemgr in the inner. This however implies a more in-depth surgery
in the outer/inner setup (to have e.g. the outer informing the inner of
its own mmap or alternatively having the inner asking the outer about the
mmap advisory).

Kludge is preferred (at least now) as this kludge is activated only
for the inner (and for darwin, but that was already like that).

Of course, this kludge does not the state of the inner aspacemgr
matching the outer and kernel state.
So, other problems might be detected e.g. if inner aspacemgr does a check
comparing its status with kernel status.

The patch also ensures the inner reports the memory status of the
outer (using a client request) when an out of memory situation is detected.
This helps understanding what goes wrong.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13495