dllmain.cpp::ProcessCodes(): Use prefix-increment instead of postfix-increment.

Renamed iterator from "i" to "iter".
cmake/platform/msvc.cmake: Fix -subsystem option.

Should be -subsystem:windows,5.01 , not -subsystem:5.01 .
cmake/platform/: Added CMAKE_SHARED_LINKER_FLAGS.

This is used for DLLs.
Set the image version for MSVC builds.

This might also work for MinGW builds, but I haven't tested it yet.

Note that the image version is limited to major.minor.

Also: Use a variable for the PDB filenames.