update error_table[] E_STRING symbols

Now the "E_STRING" errsym strings in error_table[], with exception
to the 1st E__BASE entry, all other errsym strings must match the
following regular expression:

	^E_[A-Z][A-Z0-9_]+$

Renamed "E_1OVER0" to "E_DIVBYZERO".
Renamed "E_0OVER0" to "E_ZERODIVZERO".

Makefile

@@ -3341,6 +3341,7 @@ clean:
 
 clobber: clean
 	${V} echo '=-=-=-=-= ${MAKE_FILE} start of $@ rule =-=-=-=-='
+	${RM} -f errcode${EXT}
 	${RM} -f ${SAMPLE_TARGETS}
 	${RM} -f ${SAMPLE_STATIC_TARGETS}
 	${RM} -f tags .hsrc hsrc