Merge branch 'lt/readlink'

* lt/readlink:
  combine-diff.c: use strbuf_readlink()
  builtin-blame.c: use strbuf_readlink()
  make_absolute_path(): check bounds when seeing an overlong symlink
  Make 'prepare_temp_file()' ignore st_size for symlinks
  Make 'diff_populate_filespec()' use the new 'strbuf_readlink()'
  Make 'index_path()' use 'strbuf_readlink()'
  Make 'ce_compare_link()' use the new 'strbuf_readlink()'
  Add generic 'strbuf_readlink()' helper function