NFC: Document MSVC getters on Triple
NFC: Document MSVC getters on Triple

Summary:
Document the differences between the isKnownWindowsMSVC() and isWindowsMSVC() methods on Triple.

Also removed the '\brief' Doxygen annotations - now that 'AUTOBRIEF' is set to on, they are unnecessary.

Subscribers: jfb, tberghammer, danalbert, srhines, dschuff

Differential Revision: http://reviews.llvm.org/D14110

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@253159 91177308-0d34-0410-b5e6-96231b3b80d8

GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,apple/swift-llvm,llvm-mirror/llvm,apple/swift-llvm