libpagemap: fix memory leak in pm_process_destroy()

procrank/librank not impacted because they end quickly. But other
programs that use libpagemap and last for long time can easily see this
memory leak.

Change-Id: I8c9e9444555bef9145c9d89850987a29f15a9b3b
Signed-off-by: Carton He <carton.he@marvell.com>
tests: Use -fno-strict-aliasing for memtest

There's just no way to do this piece correctly:
    int dummy = 0;
    printf("corrupting our stack...\n");
    *(volatile long long*)&dummy = 0;

Change-Id: If02ff71b3c23c3d8118694f6edba0ecf904baf8a
Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>