Introduce sane limits for memory allocations

[bk138]

There are already multiple places where expected-to-be-small allocations are checked (c5ba3fee85a7ecbbca1df5ffd46d32b92757bc2a, e34bcbb759ca5bef85809967a268fdf214c1ad2c, c2c4b81e6cb3b485fb1ec7ba9e7defeb889f6ba7), but larger allocations remain unchecked regarding plausible sizes (045a044e8ae79db9244593fbce154cdf6e843273 for instance).