- simplify column number tracking using a pointer to the beginning of line
instead of `eol` + `mark`.
- add `js_parse_error_pos` to report syntax errors with exact source position
for token parsing errors. This makes the syntax error reports much more precise.
eg: exact position of UTF-8 encoding error, invalid escape sequence, etc.
- add `JSSourcePos` type to use single opaque object for token source position
- add `emit_pos` to set the precise source position in code generation
- change `emit_op` to no longer emit source positions from `s->last_line_num` and `s->last_col_num`.
- remove `last_line_num` and `last_col_num` `JSParserState` members
- runtime errors on calls report the column number of calling function or method name.
- runtime errors on `new` expressions report the column number of the `neẁ` keyword.
- do not show source position in backtrace if debug information is missing
- fix spurious parsing bugs when `js_parse_skip_parens_token` could not reparse
the current token because of stack overflow detection.
- `js_parse_save_pos` now saves the current token and `js_parse_seek_back` always
restores the token, hence never fails, while `js_parse_seek_token` reparses the
saved token. This is needed to handle the weird semantics of `"\1"; "use strict";`
- simplify html comment detection
- update **tests/test_builtin,js** with more informative messages
- improve `assert()` and **tests/test_language.js** tests
- update **v8.txt** for updated column numbers in remaining errors
59462214cb