Mass typo fix in Makefiles

With the make indent rule there was a typo for indent as 'intent'. This
was fixed with my sgit tool like:

    sgit -e 's/no intent\( tool found\)/no indent\1/g' '*Makefile'

1993/plummer/Makefile

@@ -187,7 +187,7 @@ indent.c: ${PROG}.c
 	    echo "${INDENT} < $< > $@"; \
 	    ${INDENT} < $< > $@; \
 	else \
-	    echo "no intent tool found, ident $< yourself, sorry"; \
+	    echo "no indent tool found, ident $< yourself, sorry"; \
 	    echo "exit 17"; \
 	    exit 17; \
 	fi