Introduces one massive template for generating SourceHook managers.
The goal is for this to simplify the definition of SourceHooks long-term by replacing macros with templates.

This introduces some new templates for metaprogramming, but they're hidden away in the SourceHook::metaprogramming namespace.

Tested on Windows 32 bit and Linux 32 bit TF2.

…feat/templated-sourcehook

Sometimes my vast intellect... it scares me.

# Conflicts:
#	core/provider/source/provider_source.cpp

This allows us to specify the SH pointer and the Plugin ID pointer in the template, so when the plugin uses Hook<> it doesn't have to touch g_PLID or g_SHPtr.

Also added a little struct that wraps ISourceHook->xHookById methods.

This is a large refactor that splits our mega-template into a few smaller ones. First off, the PLUGIN_GLOBALVARS() helpers were put in the SourceHook namespace.

- HookHandlerImpl: Responsible for the lowered delegates (post-vafmt), can be used independently of other templates added here. Relies on parent HookManager class to handle the unlowered original invocation logic. (As a template parameter)
- HookCoreImpl: Adds a public interface & glue layer beterrn managers and HookHandlerImpl

- HookImpl: non-varardic hook manager
- FmtHookImpl: format-string hook manager

FmtHookImpl was tested by hooking IVEngineServer::ClientCommand.

Turns out this isn't true. Yay! Less work for me :^)

- A few style improvements
- Add & correct some documentation
- Change AddHook signature to not allow DVP as an option (for now!)
- Fix cstdio not being pulled in on linux (bleh)
- Add some more static_asserts to make errors easier to interpret (yay)

…dd blank logging