[scope] add 'scope' to delegates

[WalterBright]

This is to resolve the following -dip1000 generated errors:

src/gc/impl/conservative/gc.d(2150): Error: function core.thread.thread_scanAll (scope void delegate(void*, void*) nothrow scope scan) is not callable using argument types (void delegate(void* pbot, void* ptop) nothrow)
src/gc/impl/conservative/gc.d(2397): Error: function core.thread.thread_processGCMarks (scope int delegate(void* addr) nothrow scope isMarked) is not callable using argument types (int delegate(void* addr) nothrow)

I.e. a non-scope delegate cannot be used where a scope delegate is expected.

[WalterBright]

Auto-merge toggled on

[WalterBright]

Auto-merge toggled off

[WalterBright]

@MartinNowak ping

[MartinNowak]

Auto-merge toggled on

[MartinNowak]

Also see dlang/dmd#6495 (comment)

[WalterBright]

CyberShadow/DAutoTest is failing with the same error on every PR of mine. It's clearly something broken that has been merged in somewhere, and has nothing to do with this PR.