Revert "Generalize the remove-outputs check for fully-prunable transactions."

This reverts commit 7b3d6ef4dcb61ca20447df1e30bdad940f3882fd.
Revert "Skip unspendable outputs in consistency check"

This reverts commit 4bac0f06c121f3f5cef738da2f0e2125860652c3.
Revert "CScript::IsUnspendable method"

This reverts commit 42d0da9e5c8a4d32ec6c91f280611d6d9d9703bf.

Conflicts:
	src/script.h