Add style rule to avoid combining assignment and logical tests.

git-svn-id: svn://svn.berlios.de/openocd/trunk@2503 b42882b7-edfa-0310-969c-e2dbd0fdcd60

doc/manual/style.txt

@@ -106,6 +106,20 @@ int f(int x1, int x2)
 	int y = f(x1, x2 - x1);
 	...
 }
+@endcode
+- Separate assignment and logical test statements.  In other words, you
+should write statements like the following:
+@code
+// separate statements should be preferred
+result = foo();
+if (ERROR_OK != result)
+	...
+@endcode
+More directly, do @b not combine these kinds of statements:
+@code
+// Combined statements should be avoided
+if (ERROR_OK != (result = foo()))
+	return result;
 @endcode
 
  */