Changed the build to use /MD flag so that DDL version of C runtime is used.

To make sure MariaDB is always runnable on target system, include
redistributable CRT libraries into installer.

For MSI package, use Microsoft's merge modules.
For ZIP  use "applocal" approach,i.e place redistributable dlls
into the bin directory of the package(via InstallRequiredSystemLibraries
cmake module) The space overhead of libraries in negligible, ~ 3MB unpacked.

There are 2 cases, where we still link C runtime statically

- Upgrade wizard, it uses MFC, and we link statically to avoid
redistribute also whole MFC (for this single application, does not
make much sense).

- MSI installer's custom action dll wixca.dll.Here, we need static link
so that MSI won't fail on a target system that does not have VC++2015
runtime already installed.