The code for nested and unnested strings was mixed, thereby being too
simple for the nested case. I separated them, which is simpler than
the fixed combined version.
Detected by the macro call
..EMIT <$FAC=^D<fb$rea>>
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).
