obvious malloc -> reallocarray, for mult int oflow
obvious reallocarray(); ok doug
obvious conversion of realloc() to reallocarray().  Luckily this is
using pollfd, because if this was fd_set... it would not be obvious
(or easy)
using reallocarray() gives us multiplicative integer overflow checking
in case something wants to create massive amounts of environment, like
a bit more than 1/4 of a 32-bit address space.  unrealistic -- but why
audit one code path, and not treat others the same?  then you have to
re-engage everytime you see the code.  read the news, that isn't what
developers do.  At least if the code paths look the same, there is hope,
because they are easier to verify for correctness.  developers need
to give other developers a chance to want to care.
obvious reallocarray()
obvious realloc -> reallocarray conversion