Revert "Remove old fork-and-specialize API"

This reverts commit 5a6f4a871c6e1527e450e6f700aebce8e4e80922.
Revert "Finish fixing Zygote descriptor leakage problem"

This reverts commit 19c11a0285d6012b4e5fb0b5519dfa2616a0ce27.
Revert "Fix NewLocalRef, NewGlobalRef to handle cleared weak globals."

This reverts commit 64d7fd0b02ba7f38648e641f22416e57b42f39cd.