Macro.to_string: don't add unneeded binop parens

This changes the `Macro.to_string` output of (quoted) `1+2+3+4` from
`((1 + 2) + 3) + 4` to `1 + 2 + 3 + 4`.
Merge pull request #1606 from pminten/macro-to-string-binop-parens

Macro.to_string: don't add unneeded binop parens
Update Macro.to_string comments
Do not touch lock manifest if there is no change
Update LEGAL file
Fixed typos in Mix.Shell.Process docs
Merge pull request #1608 from jwarwick/mix_shell_process

Fixed typos in Mix.Shell.Process docs
Fixed comment typo in lib/elixir/src/elixir_translator.erl
Fix typo in CHANGELOG.md
Merge pull request #1611 from thmzlt/patch-1

Fix typo in CHANGELOG.md
Merge pull request #1610 from stratosv/patch-1

Fixed comment typo in lib/elixir/src/elixir_translator.erl
Do not show dest info when comparing deps
Always stop on --, even for parse
Rely on :binary.part since we are using :binary prefix functions
Add underscore for avoiding variable unused warning
Remove unecessary modules from docs
Merge pull request #1616 from parroty/patch-1

Add underscore for avoiding variable unused warning
Allow erlang options when compiling elixir regexes
Improve warning for ungrouped clauses
Allow << _ :: utf8 >> <> binary in matches, closes #1619