[CMake] fool-proofing configure.cmd for msvs

[CMAKE]
Add some fool-proofing to configure.cmd related to MSVS:
-VSSolution switch now outputs to a dedicated folder if running from source directory.
-Give an error if the user is trying to mix ninja and VSSolution in the same output directory.
-In a MingW environment, give an error on VSSolution switch and give a warning on RTC switch.
Fix -DNEW_STYLE_BUILD=0 option.

Configure.cmd can cause a lot of trouble if you don't know what you're doing. This update eliminates a lot of potential for user error. See my forum post for more info.