Case insensitivity of the import statement

[timmy-newtron]

The import statement allowed import of files without checking for cases in file names. This branch should fix the issue (by aborting translation when the name of the import file is unequal to the file name of the imported module itself) and introduce an according test scenario.

[b-studios]

@edding4500 the CI test fails on unix systems since there it (apparently) already has the desired semantics.

It is a bit fragile, but you could change the error message to 'Cannot find source for examples/pos/liStS" to match the behavior on unix.

Vice versa you could also try to make the Unix version report a better error.

[b-studios]

Superseded by #158