[librsvg] (10 commits) ...Merge github.com:alatiera/librsvg - optimize xml:space normalization

[Federico Mena Quintero <federico src gnome org>]

Summary of changes:

  24b41fa... Replace split/filter on ' ' || '/t' with .split_whitespace 
  4118f41... Reduce extra allocations by using itertools::join instead o
  cef86a9... Use str.replace() instead of map/match/collect .
  4a6be7c... Change the signature of the whitespace normalizer functions
  4e79a87... Use str.replace() instead to convert newlines into spaces.
  2409c58... Properly revert reggresions this time.
  7edfd2c... Reduce allocations in whitespace normalize_default.
  6fc8583... Added extra test cases.
  68536fb... Remove borrow::Cow usage since it's not really helpfull.
  6908ba1... Merge github.com:alatiera/librsvg - optimize xml:space norm