Fix formatting edits for CRLF files and files without trailing newline

[mattn]

Two formatting bugs around line endings:

• Formatter output had all \r stripped but was then diffed against the original CRLF text, so on CRLF files every line appeared changed and even a no-op format produced whole-file edits with mixed line endings. Restore CRLF in the output before diffing when the original uses it.
• When the document does not end with a newline, ComputeEdits emitted ranges referencing the nonexistent line past the end; clients clamp such out-of-spec positions inconsistently, producing the stray blank lines reported in Unexpected newline at the end of file when formatting it #241/Erroneous newlines using efm in neovim #181. Clamp those positions to the end of the last line.

Adds tests that verify the produced edits apply cleanly. Fixes #241. Fixes #181.