Dfl Win64 support

# Win64 support

## Goal
1. Minimal patches.
2. No breaking change to win32 programs.

## Fix compile error
Fix Dozens of size_t conversion error.

Add toI32 helper function instead of type cast.

Especially, collection helpers are rather complicated.

## Fix runtime error
### Update WIn32 APIs
1. SetWindowLong family.
SetWindowLong -> SetWindowLongPtr, and so on.
2. Common dialogs: structures and callbacks.
UINT -> UINT_PTR, and so on.
3. Windows timer functions: callbacks.

### Fix application manifest
embedded in dfl/application.d.

## Fix Toolchain
### Add makewin64.bat
It requires fix by each user -- MSVC paths.

It is not called by go.bat. (But maybe it should be...)
### Fix dfl.exe
Switch linker flags when -m64 specified.