Merge branch '2.4.x' into 2.5.x

Merge branch '2.4.x' into 2.5.x

* 2.4.x:
  rand/rand.c: Mix the pool key in `rand_gate' and `rand_stretch'.
  rand/lcrand.c: Swap flags and max so generator not advertised as strong.
  pub/dh-kcdsa.c: Free the correct factor.
  math/limlee.c: Don't leak the factor vector on overall failure.
  math/limlee.c: Handle an abort from `pgen' correctly.
  math/pgen.c: Don't free the tester if it's not set up.
  math/ec-exp.h: Fix segfault when base point is at infinity.
  key/key-data.c (key_copydata): Fix catastrophic bug.
  key/key-data.c (key_split): Fix long-standing reference leak.
  key/key-misc.c (key_bytag): Don't give up because a by-id search fails.
  base/dispatch.c, etc.: Check that `rdrand' works.