Update libev sources to 4.22

Update libev sources to 4.22

This update fixes a memory leak when freeing null pointers using
ev_realloc_emul().  In 4.04, that function assumed that realloc(x, 0)
is equivalent to free(x) under glibc, but in at least some versions of
glibc, realloc(NULL, 0) behaves like malloc(0) rather than free(NULL)
and allocates memory.

ticket: 8436 (new)