move some rules into 1337.mk

A number of rules have been moved from entry `Makefile`s into the
`1337.mk` include file to make it easier for these common rules to be
updated or modified globally (by modifying the `1337.mk` include file).

The entry level `Makefile`s are now similar in form to the
/Makefile.example](https://github.com/ioccc-src/mkiocccentry/blob/master/Makefile.example)
file from the other repo.

The following make rules were moved into the `1337.mk` include file:

- `make indent.c`
- `make install`
- `make diff_orig_prog`
- `make diff_prog_orig`
- `make diff_alt_prog`
- `make diff_prog_alt`

This simplifies the entry level `Makefile`s so that they mostly reflect
the specifics of the particular entry.

Mentioned in FAQ 4.2, that the make diff rules are in the `1337.mk` include file.

Fixed invalid TAB character in `faq.md`.

Removed `make clean` directives that removed `indent.c`.  This file is now
removed via `make indent_clean`, a clean rule that also removes `indent.c`.

Removed `make clobber` directives that removed sandwich,  This file is now
removed via `make indent_clobber`, a clean rule that also removes `sandwich`.

Added `make indent_clean` and `make indent_clobber` rules into the top level
`Makefile` and the year level `YYYY/Makefile`.

Performed `make quick_www` to accomplish the above and to test under macOS.

Makefile

@@ -260,30 +260,6 @@ clobber:
         done
 	@echo '=-=-=-=-= IOCCC complete make $@ =-=-=-=-='
 
-install:
-	@echo '=-=-=-=-= IOCCC begin make $@ =-=-=-=-='
-	@-for i in ${YEARS}; do \
-	    if [[ -f $$i/Makefile ]]; then \
-		echo "cd $$i; make $@"; \
-		(cd $$i; make $@); \
-	    else \
-		echo "Warning: $$i/Makefile not found, skipping $$i for $@ processing" 1>&2 ; \
-	    fi; \
-        done
-	@echo '=-=-=-=-= IOCCC complete make $@ =-=-=-=-='
-
-indent.c:
-	@echo '=-=-=-=-= IOCCC begin make $@ =-=-=-=-='
-	@-for i in ${YEARS}; do \
-	    if [[ -f $$i/Makefile ]]; then \
-		echo "cd $$i; make $@"; \
-		(cd $$i; make $@); \
-	    else \
-		echo "Warning: $$i/Makefile not found, skipping $$i for $@ processing" 1>&2 ; \
-	    fi; \
-        done
-	@echo '=-=-=-=-= IOCCC complete make $@ =-=-=-=-='
-
 
 #################################
 # IOCCC website maintenance rulz
@@ -851,6 +827,63 @@ genpath_top:
 	@echo '=-=-=-=-= IOCCC complete make $@ =-=-=-=-='
 
 
+########################
+# extended utility rules
+########################
+
+.PHONY: indent_clean indent_clobber
+
+# you may be able to misunderstand the source by reading indent.c
+#
+indent.c:
+	@echo '=-=-=-=-= IOCCC begin make $@ =-=-=-=-='
+	@-for i in ${YEARS}; do \
+	    if [[ -f $$i/Makefile ]]; then \
+		echo "cd $$i; make $@"; \
+		(cd $$i; make $@); \
+	    else \
+		echo "Warning: $$i/Makefile not found, skipping $$i for $@ processing" 1>&2 ; \
+	    fi; \
+        done
+	@echo '=-=-=-=-= IOCCC complete make $@ =-=-=-=-='
+
+indent_clean: clean
+	@echo '=-=-=-=-= IOCCC begin make $@ =-=-=-=-='
+	@-for i in ${YEARS}; do \
+	    if [[ -f $$i/Makefile ]]; then \
+		echo "cd $$i; make $@"; \
+		(cd $$i; make $@); \
+	    else \
+		echo "Warning: $$i/Makefile not found, skipping $$i for $@ processing" 1>&2 ; \
+	    fi; \
+        done
+	@echo '=-=-=-=-= IOCCC complete make $@ =-=-=-=-='
+
+indent_clobber: indent_clean clobber
+	@echo '=-=-=-=-= IOCCC begin make $@ =-=-=-=-='
+	@-for i in ${YEARS}; do \
+	    if [[ -f $$i/Makefile ]]; then \
+		echo "cd $$i; make $@"; \
+		(cd $$i; make $@); \
+	    else \
+		echo "Warning: $$i/Makefile not found, skipping $$i for $@ processing" 1>&2 ; \
+	    fi; \
+        done
+	@echo '=-=-=-=-= IOCCC complete make $@ =-=-=-=-='
+
+install:
+	@echo '=-=-=-=-= IOCCC begin make $@ =-=-=-=-='
+	@-for i in ${YEARS}; do \
+	    if [[ -f $$i/Makefile ]]; then \
+		echo "cd $$i; make $@"; \
+		(cd $$i; make $@); \
+	    else \
+		echo "Warning: $$i/Makefile not found, skipping $$i for $@ processing" 1>&2 ; \
+	    fi; \
+        done
+	@echo '=-=-=-=-= IOCCC complete make $@ =-=-=-=-='
+
+
 #############################################################
 # NOTE: 'Don't Panic' if you don't understand the stuff below
 #############################################################