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.

faq.md

@@ -472,7 +472,7 @@ For example:
             cp -f prog $@
 
     clean:
-	    rm -f prog.o
+            rm -f prog.o
 
     clobber: clean
             rm -f desired_name
@@ -3940,6 +3940,17 @@ very easily. To do that `cd 1991/dds` and then do:
 
 and you'll see a single line changed and very simply.
 
+**NOTE**: The above mentioned `make` rules are located in the [1337.mk](%%REPO_URL%%/1337.mk)
+include Makefile via the optional include directive line:
+
+``` <!---Makefile-->
+    -include 1337.mk ../1337.mk ../../1337.mk
+```
+
+The [1337.mk](%%REPO_URL%%/1337.mk) file must exist in the current
+directory, or under the directory above, or under the directory 2 levels
+above in order for these rules to work.
+
 
 #### Tip: if you have `colordiff` installed it's a lot easier to see the differences
 
@@ -3958,6 +3969,8 @@ See the
 FAQ on "[original source code](#original_source_code)"
 for more information.
 
+Jump to: [top](#)
+
 
 <div id="faq4_3">
 ###  FAQ 4.3  - Why do author remarks sometimes not match the source and/or why are there other inconsistencies with the original entry?