DebugInfo: add explicit casts for -Wqual-cast
DebugInfo: add explicit casts for -Wqual-cast

Fix a warning detected by gcc 6:
  warning: cast from type 'const void*' to type 'uint8_t* {aka unsigned char*}' casts away qualifiers [-Wcast-qual]

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@290618 91177308-0d34-0410-b5e6-96231b3b80d8

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