libhpcalcs: portable (Windows / MacOS X / Linux) connectivity kit library

[debrouxl]

The non-functional changes have been committed to the master branch.
I have rebased master2, where the untested commit for adding tentative IDs for .hpappnote and .hpappprgm is, onto master, so you can use that if you want to test .hpappprgm

I hope that .hpappprgm won't have the same aforementioned problem as .hpprgm. That said, for the narrow purposes of confirming the internal IDs for the .hpappnote and .hpappprgm files (probably 7 and 8), the test would be successful upon proper creation of a file of the corresponding type, no matter what the file's actual contents are, on the computer and calculator side.