Add srcloc to snippet parse error message

Snippet modules that has parse errors now shows line and column numbers.

Not sure if this is meant to be used this way, but I had a tool on-demand compiles a module (passed in as a snippet) that generates a diagram, and I found the parse errors in this module did not show line numbers.

Tested by patching the hackage version with this diff, and verified that parse errors did show source loc.