The original intent of the code, when faced with something like
.MACRO A
.MACRO B
.ENDM A
is to terminate the outer macro definition immediately.
However some macros redefine themselves, and that broke.
For now, detect self-redefinition and disable the early
end if there is one.
Since this does not match what's described on page 7-3,
this will change if it doesn't break my test cases.
Also, to make Kermit sources work, only increase the local symbol block
counter if there actually was a local symbol used in the block.
This way, conditional inclusions (which include source text only in the
first pass) will have less potential for de-synchronisation between the
passes. After all, if the generated internal local symbol names do
not match, phase errors will result (showing themselves as strange label
redefinition problems).
