[llvm-dwarfdump] Print type names in DW_AT_type DIEs

This patch adds printing for DW_AT_type DIEs like it is already the case
for DW_AT_specification DIEs. This is a rather naive approach and only a
start. We should have pretty printers for different languages.

Differential revision: https://reviews.llvm.org/D36993

llvm-svn: 315297