FMSLogo Code

Partially fix bug #546; throw errors from NET* instead of a showing a modal dialog
This includes all error conditions that are programming errors for FMSLogo (not the real network errors).

I removed the errors when calling NETCONNECTOFF and NETACCEPTOFF and instead made it a no-op. This removed two strings that would had to have been translated and makes it easier for the programmer to cleanup.

Require strict case equality when checking error messages

Remove unneeded backslashes in regular expressions

Add bad input tests for the NET* procedures.
This is preparation for fixing Bug #546.

Add self-tests for the testlib procedure FILEEXISTS

Add a regression test that BITSAVE overwrites an existing file

Enable MOUSEPOS on GNU/Linux.
The rest of the mouse subsystem is functional on GNU/Linux so there was no reason for it to output [].

Cleanup: Move the prefixing of "MIDI Error: " from mklocal.pl to localizedstrings.txt
This improves tracability because the text in localizedstring.txt is now what is used by FMSLogo.
This also enables a translator to come up with a better error message, if the prefix is redundant.

Cleanup: Append ": %s" to LOCALIZED_ERROR_MCI instead of in mklocal.pl
This simplifies mklocale.pl by removing a special case that fabricated the format string.
It also makes it possible for a translator to come up with a better format string.

Change the size of the buffer given to mciGetErrorString to 128.
This matches the documented maximum size of any error string.