add tool to sort .gitignore content

We sort with lines starting with # first.
We sort with lines starting with * second.
We sort with lines that do not start with [#!*] third.
We sort with lines starting with ! fourth.

Example usage in vim with a keyboard macro <escape>f:

```vim
:map ^[f 1G!G../../bin/sgi^M
```

 or via .vimrc:

```vimrc
" sort the entire .gitignore file using ../../bin/sgi
:map  ^[f 1G!G../../bin/sgi^M
```

 NOTE: The ^[ above is ((Escape)) and ^M is ((Control-M)).

Example usage in shell:

```sh
rm -f t && ../../bin/sgi < .gitignore > t && mv -f t .gitignore
```

Suggested usage:

```sh
bin/all-run.sh bin/sort.gitignore -v 1
```

Sorted all winner .gitignore according to this method.
Sorted all year level .gitignore according to this method.
Sorted top level .gitignore according to this method.

2006/birken/.gitignore

@@ -1,8 +1,8 @@
 #
-# sort with: sort -d -u
+# sort with: ../../bin/sgi
+*.dSYM
 birken
 birken.orig
-*.dSYM
 indent
 indent.c
 indent.o

2006/borsanyi/.gitignore

@@ -1,9 +1,9 @@
 #
-# sort with: sort -d -u
-borsanyi
-borsanyi.orig
+# sort with: ../../bin/sgi
 *.dSYM
 *.gif
+borsanyi
+borsanyi.orig
 indent
 indent.c
 indent.o

2006/grothe/.gitignore

@@ -1,5 +1,5 @@
 #
-# sort with: sort -d -u
+# sort with: ../../bin/sgi
 *.dSYM
 grothe
 grothe.orig

2006/hamre/.gitignore

@@ -1,5 +1,5 @@
 #
-# sort with: sort -d -u
+# sort with: ../../bin/sgi
 *.dSYM
 hamre
 hamre.orig

2006/meyer/.gitignore

@@ -1,5 +1,5 @@
 #
-# sort with: sort -d -u
+# sort with: ../../bin/sgi
 *.dSYM
 indent
 indent.c

2006/monge/.gitignore

@@ -1,5 +1,5 @@
 #
-# sort with: sort -d -u
+# sort with: ../../bin/sgi
 *.dSYM
 indent
 indent.c

2006/night/.gitignore

@@ -1,5 +1,5 @@
 #
-# sort with: sort -d -u
+# sort with: ../../bin/sgi
 *.dSYM
 indent
 indent.c

2006/sloane/.gitignore

@@ -1,5 +1,5 @@
 #
-# sort with: sort -d -u
+# sort with: ../../bin/sgi
 *.dSYM
 indent
 indent.c

2006/stewart/.gitignore

@@ -1,12 +1,12 @@
 #
-# sort with: sort -d -u
+# sort with: ../../bin/sgi
 *.dSYM
+*.png
+*.xbm
 indent
 indent.c
 indent.o
-*.png
 prog.orig
 stewart
 stewart.html
 stewart.orig
-*.xbm

2006/sykes1/.gitignore

@@ -1,7 +1,7 @@
 #
-# sort with: sort -d -u
-cube.gif
+# sort with: ../../bin/sgi
 *.dSYM
+cube.gif
 indent
 indent.c
 indent.o

2006/sykes2/.gitignore

@@ -1,5 +1,5 @@
 #
-# sort with: sort -d -u
+# sort with: ../../bin/sgi
 *.dSYM
 indent
 indent.c

2006/toledo1/.gitignore

@@ -1,5 +1,5 @@
 #
-# sort with: sort -d -u
+# sort with: ../../bin/sgi
 *.dSYM
 indent
 indent.c

2006/toledo2/.gitignore

@@ -1,5 +1,6 @@
 #
-# sort with: sort -d -u
+# sort with: ../../bin/sgi
+*.dSYM
 ADVENTUR/
 BASICS/
 C
@@ -17,7 +18,6 @@ WS33/
 WS33-1/
 WS33-2/
 WS33-KPR/
-*.dSYM
 indent
 indent.c
 indent.o

2006/toledo3/.gitignore

@@ -1,5 +1,5 @@
 #
-# sort with: sort -d -u
+# sort with: ../../bin/sgi
 *.dSYM
 indent
 indent.c