Count non-ASCII characters correctly for column numbers

[strager]

quick-lint-js gives incorrect column numbers when the source code contains non-ASCII characters:

/*☃*/x

Expected:

$ ./build/quick-lint-js hello.js
hello.js:1:6: error: use of undeclared variable: x

Observed:

$ ./build/quick-lint-js hello.js
hello.js:1:8: error: use of undeclared variable: x

quick-lint-js' locator should count ☃ as one column, not three.

• CLI
• WASM demo
• LSP
• Vim

[strager]

• CLI: Count bytes, like GCC and Clang do. Tested in commit 4c2383d. Newline handling untested.
• WASM demo: Count UTF-16 code units. Implemented in commit bb83ba4.
• LSP: Count UTF-16 code units. Implemented in commit ee99deb.
• Vim: Count bytes. Tested in commit edcf38e. Newline handling poorly tested.