AP_OSD: Simplify with the code enumerate()

* Avoid hardcoding the path to the python executable on the shebang line
* Using __with open() as__ automates file close().

libraries/AP_OSD/fonts/mcm2bin.py

@@ -1,21 +1,17 @@
-#!/usr/bin/python
-import sys;
+#!/usr/bin/env python
+import sys
 
 if len(sys.argv) < 3:
-   print "Usage: ./mcm2bin.py clarity.mcm  clarity.bin"
+   print("Usage: ./mcm2bin.py clarity.mcm  clarity.bin")
    exit()
 
 with open(sys.argv[1]) as inp:
     content = inp.readlines()
-inp.close();
 
 content.pop(0)
 
-out = open(sys.argv[2], 'wb')
-i = -1
-for line in content:
-    i = i + 1
+with open(sys.argv[2], 'wb') as out:
+    for i, line in enumerate(content):
         if i % 64 < 54:
            b = int(line, 2)
            out.write(bytearray([b]))
-out.close()