python: Fix rich comparisons

Python 3 doesn't call objects __cmp__() methods any more to compare
them. Instead, it requires implementing the rich comparison methods
explicitly: __eq__(), __ne(), __lt__(), __le__(), __gt__() and __ge__().

Fortunately Python 2 also supports those.

This commit only implements the comparison methods which are actually
used by the build scripts.

Signed-off-by: Mathieu Bridon <bochecha@daitauha.fr>
Reviewed-by: Dylan Baker <dylan@pnwbakers.com>

src/mapi/mapi_abi.py

@@ -121,19 +121,18 @@ class ABIEntry(object):
     def __str__(self):
         return self.c_prototype()
 
-    def __cmp__(self, other):
+    def __lt__(self, other):
         # compare slot, alias, and then name
-        res = cmp(self.slot, other.slot)
-        if not res:
+        if self.slot == other.slot:
             if not self.alias:
-                res = -1
+                return True
             elif not other.alias:
-                res = 1
+                return False
 
-            if not res:
-                res = cmp(self.name, other.name)
+            return self.name < other.name
+
+        return self.slot < other.slot
 
-        return res
 
 def abi_parse_xml(xml):
     """Parse a GLAPI XML file for ABI entries."""