- Move NewEnvListVar to pkg/eval/vars.
- De-export GlobPattern, GlobFlag and ExternalCmd.
- Merge editor.go and chdir.go into eval.go, value_helper.go into compile_value.go.
- Remove eval_internal_test.go and replace it with a new test for $pid.
Not sure what happened but my fix for issue #1120 resulted in the core
unit test module not being executed due to a bogus "// +build wtf"
comment. Apparently I was experimenting with "+build" directives and
forgot to remove that line. This also improves the test coverage of the
$pwd code from 44% to 100%.
