bpo-15999: Clean up of handling boolean arguments. (GH-15610)

* Use the 'p' format unit instead of manually called PyObject_IsTrue().
* Pass boolean value instead 0/1 integers to functions that needs boolean.
* Convert some arguments to boolean only once.
diff --git a/Lib/quopri.py b/Lib/quopri.py
index cbd979a..08899c5 100755
--- a/Lib/quopri.py
+++ b/Lib/quopri.py
@@ -204,11 +204,11 @@
         print("-t: quote tabs")
         print("-d: decode; default encode")
         sys.exit(2)
-    deco = 0
-    tabs = 0
+    deco = False
+    tabs = False
     for o, a in opts:
-        if o == '-t': tabs = 1
-        if o == '-d': deco = 1
+        if o == '-t': tabs = True
+        if o == '-d': deco = True
     if tabs and deco:
         sys.stdout = sys.stderr
         print("-t and -d are mutually exclusive")