Precise location for mutation

[programLyrique]

The mutation is located and reported using source references. They are attached to braces and so are not very precise to locate the line and column of a mutation in a block of more than one line.

Some ideas:

• use the parse data (getParseData) instead of the source references
• build more precise source references, using imputsrcref
• do not use the R parser at all but tree-sitter (faster also probably)