Output file name and line number (varcheck and defercheck)
Use ast.IsExported func
Improve structcheck (see details below); modify README.md

1. Output file name and line number
2. Handle struct literals with positional field values
3. Remove -n option
Add license headers
Add support for multiple packages at the cmd line and glob support (closes #2; closes #3)
Correct the README
Add fourth argument to the call of LookupFieldOrMethod (fixes #7)
Add cgo support (fixes #4)
Use kisielk/gotool instead of opennota/glob