Expand all leading tabs in markdown files

Given how problematic leading tabs in markdown files can be,
we have expanded all leading tabs in markdown files by:

```sh
find * -type f -name '*.md' -print |
  while read -r file; do
    rm -f "$file.tmp" ;
    expand < "$file" > "$file.tmp" ;
    mv -f -v "$file.tmp" "$file" ;
  done
```

Given the previous changes to `bin/pandoc-wrapper.sh` and other recent
commits and recent pull requests, the were were **NO** changes to
any HTML files.  This is a **good thing** as the expression goes.

No there are no leading tabs in any markdown files.
A check to catch any re-introduction of leading tabs
into any markdown file is on the way.

BTW: We do not have anything against leading tabs in files,
even though we have had to deal with their impact on forming
HTML from markdown files (as well as the calc source code).
It is just that this is one of those cases where tabs conflict
(sometimes caused by people wanting to change the classic
8-space tab model) with a desired outcome.

Perform `make www` to perform the above and test under macOS.

2004/vik2/README.md

@@ -62,21 +62,21 @@ The ALU has six instructions:
 - `CLR_Y` - Clear [register](https://en.wikipedia.org/wiki/Processor_register) `Y`.
 
 - `ADD`   - Calculates `X` + `Y` and stores the result in `X`. If the result
-	    is larger than 11 bits, the [CARRY
-	    bit](https://en.wikipedia.org/wiki/Carry_flag) in `SR` is set otherwise
-	    the `CARRY` bit is cleared.
+            is larger than 11 bits, the [CARRY
+            bit](https://en.wikipedia.org/wiki/Carry_flag) in `SR` is set otherwise
+            the `CARRY` bit is cleared.
 
 - `SUB`   - Calculates `X` - `Y` and stores the result in `X`. If `Y` was larger
-	    than `X`, the [CARRY bit](https://en.wikipedia.org/wiki/Carry_flag)
-	    in `SR` is set otherwise the `CARRY` bit is cleared.
+            than `X`, the [CARRY bit](https://en.wikipedia.org/wiki/Carry_flag)
+            in `SR` is set otherwise the `CARRY` bit is cleared.
 
 - `TST`   - If `X` == `Y` the `EQ` bit in `SR` is set, otherwise the `EQ` bit is
-	    cleared. If `X` < `Y` the `LT` bit in `SR` is set, otherwise the `LT`
-	    bit is cleared.
+            cleared. If `X` < `Y` the `LT` bit in `SR` is set, otherwise the `LT`
+            bit is cleared.
 
 - `INC2`  - Calculates `X` + 2 and stores the result in `X`. The [CARRY
-	    bit](https://en.wikipedia.org/wiki/Carry_flag) is handled as in the
-	    `ADD` instruction.
+            bit](https://en.wikipedia.org/wiki/Carry_flag) is handled as in the
+            `ADD` instruction.
 
 Internally the [ALU](https://en.wikipedia.org/wiki/Arithmetic_logic_unit)
 implements a one bit adder with a carry in and carry out. This adder is the core
@@ -209,7 +209,7 @@ taken to pre-process the program were measured using GNU `cpp` on my 2.0MHz P4
 with 512Mb ram and a lot of disk.
 
 ```
-	    Generated   Recursive  Max nest  Intermediate
+            Generated   Recursive  Max nest  Intermediate
     Level   prime nrs   includes   count     file size          Time
 
       _3     < 8           2 322       9         74 748            4"
@@ -221,7 +221,7 @@ with 512Mb ram and a lot of disk.
       _9     < 512     1 920 272      38     65 527 808(*)  1h 42'19"(*)
      _10     < 1024    6 826 389     114     63 782 912(*)  2h 47'58"(*)
 
-	 (*) Before cpp crashed.
+         (*) Before cpp crashed.
 ```