Derive MDNode from MetadataBase instead of Constant. Emit MDNodes into METADATA_BLOCK in bitcode file.

llvm-svn: 76834

llvm-svn: 75703

  !0 = constant metadata !{...}

llvm-svn: 75057

Simplify MDNode printing.

llvm-svn: 75053

llvm-svn: 72610

Constant* in preperation of a future change to support holding non-Constants
in an MDNode.

llvm-svn: 71407

llvm-svn: 68668

Constant, MDString and MDNode which can only be used by globals with a name
that starts with "llvm." or as arguments to a function with the same naming
restriction.

llvm-svn: 68420