Cygwin: cygheap: make bucket_val a static const array

Cygwin: cygheap: make bucket_val a static const array

Every time the cygheap is initialized, that is, on each fork
or exec, cygheap_init() *again* computes the bucket size values
and stores them in the cgyheap, albeit they are always the
same values anyway.

Make bucket_val a local const array, statically initialized
instead.

Fixes: 61522196c715 ("* Merge in cygwin-64bit-branch.)"
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>