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.

2013/.gitignore

@@ -1,4 +1,4 @@
 #
-# sort with: sort -d -u
+# sort with: ../bin/sgi
 iocccsize
 iocccsize.o

2013/birken/.gitignore

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

2013/cable1/.gitignore

@@ -1,8 +1,8 @@
 #
-# sort with: sort -d -u
+# sort with: ../../bin/sgi
+*.dSYM
 cable1
 cable1.orig
-*.dSYM
 indent
 indent.c
 indent.o

2013/cable2/.gitignore

@@ -1,8 +1,8 @@
 #
-# sort with: sort -d -u
+# sort with: ../../bin/sgi
+*.dSYM
 cable2
 cable2.orig
-*.dSYM
 hello
 indent
 indent.c

2013/cable3/.gitignore

@@ -1,9 +1,9 @@
 #
-# sort with: sort -d -u
+# sort with: ../../bin/sgi
+*.dSYM
 cable3
 cable3.orig
 cable.alt
-*.dSYM
 indent
 indent.c
 indent.o

2013/dlowe/.gitignore

@@ -1,8 +1,8 @@
 #
-# sort with: sort -d -u
+# sort with: ../../bin/sgi
 1.txt
-2.txt
 *.dSYM
+2.txt
 dlowe
 dlowe.orig
 fun

2013/endoh1/.gitignore

@@ -1,5 +1,5 @@
 #
-# sort with: sort -d -u
+# sort with: ../../bin/sgi
 *.dSYM
 echo
 endoh1

2013/endoh2/.gitignore

@@ -1,5 +1,5 @@
 #
-# sort with: sort -d -u
+# sort with: ../../bin/sgi
 *.dSYM
 endoh2
 endoh2.orig

2013/endoh3/.gitignore

@@ -1,10 +1,10 @@
 #
-# sort with: sort -d -u
+# sort with: ../../bin/sgi
 *.dSYM
+*.wav
 endoh3
 endoh3.orig
 indent
 indent.c
 indent.o
 prog.orig
-*.wav

2013/endoh4/.gitignore

@@ -1,5 +1,5 @@
 #
-# sort with: sort -d -u
+# sort with: ../../bin/sgi
 *.dSYM
 endoh4
 endoh4.orig

2013/hou/.gitignore

@@ -1,9 +1,9 @@
 #
-# sort with: sort -d -u
+# sort with: ../../bin/sgi
+*.dSYM
 4old_default.ppm
 a
 a.c
-*.dSYM
 hou
 hou.orig
 hou.tmp

2013/mills/.gitignore

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

2013/misaka/.gitignore

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

2013/morgan1/.gitignore

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

2013/morgan2/.gitignore

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

2013/robison/.gitignore

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