compiler: Improve location info for function parameters.
compiler: Improve location info for function parameters.

Previously, errors reported for function parameters would point to the
beginning of the function declaration instead of to the column for the
given parameter.

Change-Id: I9773783ddaf08c809e37aadb017609769cb60a0c
Reviewed-on: https://go-review.googlesource.com/11580
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

qskycolor/gofrontend,qskycolor/gofrontend,qskycolor/gofrontend,qskycolor/gofrontend,qskycolor/gofrontend,golang/gofrontend,golang/gofrontend,qskycolor/gofrontend,qskycolor/gofrontend,golang/gofrontend,golang/gofrontend