potential crashes due to code gen corner cases

[evancz]

This is a meta issue for organizing things more clearly. If you'd like to add to it, open a separate issue.

• Need to escape "</script>" - String literal containing closing script tag makes generated HTML blow up elm-lang/elm-make#174
• Capturing variables with closures in TCO - Wrong values computed due to missing scoping in translation of tail recursive code with lambdas #1287
• Variables like x² create bad code - Elm allows invalid JavaScript identifier names; runtime failure #710
• Scoping problem with shadowed variables - shadowed variable can lead to runtime error in generated JS #1359
• Local operators are not local - Wrong compilation of local operator definitions #1345
• Cannot use package names with dots - Repository names with . generate invalid JS #1406
• field' is sent through ports with the prime - Quote (prime) in record field name sent through port causes JS SyntaxError #1414