FMSLogo Code

Add a newline to end of LOCALIZED_ERROR_NETWORKSHUTDOWN
Without this, the error message doesn't appear in red (or on a separate line)
I also moved this to after the other network errors to emphasize that it's different (it needs a newline whereas the others don't).

Partially fix bug #546; throw a "general network" error for errors coming from the winsock API
Before it showed a model dialog box and threw a stopping error.
I removed the name of the WinSock function from the error message because it's not something the Logo programmer calls and the error message should be good enough to figure out which C function failed.

Cleanup: Remove unneeded #includes

Fix a build break when not using precompiled headers.

Partially fix bug #546; print async errors from network instead of a showing a modal dialog

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