more test & chunk on realloc

Signed-off-by: Wilfried Chauveau <ithinuel@gmail.com>
some work on realloc

Signed-off-by: Wilfried Chauveau <ithinuel@gmail.com>
memmgr: factorize availablity condition.

Signed-off-by: Wilfried Chauveau <ithinuel@gmail.com>