FMSLogo Code

Remove an unneeded "check_throwing" from lcount()

Add regression tests for COUNT

Add some additional bad input tests to DLLCALL.
These cover new logic added for supporting Unicode.

Replace make_strnode with make_static_strnode where appropriate.
This is slightly faster and uses slightly less memory.

Add a function comment to make_static_strnode()

Remove redundant computation from mend_nosemi()

Remove some redundant computation from mend_strnzcpy

Remove some redundant computation from clearvbar_strncmp

Rename "noparity" to "clearvbar" for clarity.

The "no parity" dates back to when UCBLogo was pure ASCII and the backslashed-ness of a character was stored in the high bit of an 8-bit byte, sometimes called the "partiy bit" when dealing with hardware. However, FMSLogo has never used the "parity" bit for this and instead marked a backslashed character by moving character to a different place in the ASCII code page (analogous to shifting them all to 128-255 by setting the high bit). Now that FMSLogo uses Unicode, it's even further removed from using a "parity" bit, as the characters are now moved to a "private use area" of Unicode.

Refactoring: Extract a global variable UTF8_BOM
This is a clearer name than "buffer".
The linker should remove duplicates.