[TableGen] Move determination of IsIsolatedToken into the tokenizer instead of trying to search characters around the token. No functional change intended. Verified for in-tree targets.
[TableGen] Move determination of IsIsolatedToken into the tokenizer instead of trying to search characters around the token. No functional change intended. Verified for in-tree targets.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@256660 91177308-0d34-0410-b5e6-96231b3b80d8

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