Changes since last update:
- Enhance inode fork verifiers to prevent loading of corrupted metadata.
- Fix a crash when we try to convert extents format inodes to btree
  format, we run out of space, but forget to revert the in-core state
  changes.
- Fix file size checks when doing INSERT_RANGE that could cause files
  to end up negative size if there previously was an extent mapped at
  s_maxbytes.
- Fix a bug when doing a remove-then-add ATTR_REPLACE xattr update where
  we forget to clear ATTR_REPLACE after the remove, which causes the
  attr to be lost and the fs to shut down due to (what it thinks is)
  inconsistent in-core state.