Update ruby-parser package to 3.15.0.
=== 3.15.0 / 2020-08-31
* 1 major enhancement:
* Added tentative 2.7 support.
* 1 minor enhancement:
* Improved ruby_parse_extract_error's handling of moving slow files out.
* 22 bug fixes:
* Bumped ruby version to include 3.0 (trunk).
* Fix an error related to empty ensure bodies. (presidentbeef)
* Fix handling of bad magic encoding comment.
* Fixed SystemStackError when parsing a huoooge hash, caused by a splat arg.
* Fixed a number of errors parsing do blocks in strange edge cases.
* Fixed a string backslash lexing bug when the string is an invalid encoding. (nijikon, gmcgibbon)
* Fixed bug assigning line number to some arg nodes.
* Fixed bug concatinating string literals with differing encodings.
* Fixed bug lexing heredoc w/ nasty mix of \r\n and \n.
* Fixed bug lexing multiple codepoints in \u{0000 1111 2222} forms.
* Fixed bug setting line numbers in empty xstrings in some contexts.
* Fixed edge case on call w/ begin + do block as an arg.
* Fixed handling of UTF BOM.
* Fixed handling of lexer state across string interpolation braces.
* Fixed infinite loop when lexing backslash+cr+newline (aka dos-files)
* Fixed lambda + do block edge case.
* Fixed lexing of some ?\M... and ?\C... edge cases.
* Fixed more do/brace block edge case failures.
* Fixed parsing bug where splat was used in the middle of a list.
* Fixed parsing of interpolation in heredoc-like strings. (presidentbeef)
* Fixed parsing some esoteric edge cases in op_asgn.
* Fixed unicode processing in ident chars so now they better mix.
60f79d5c99