vulkan/opengl: rename some vars and comments

Fixes: 159027425
Test: ./vulkan/scripts/code_generator.py and build
Change-Id: I23524a0c65d0c7c31e4dc3859ce7b979f9093553
diff --git a/vulkan/scripts/generator_common.py b/vulkan/scripts/generator_common.py
index cf370fa..ef0719d 100644
--- a/vulkan/scripts/generator_common.py
+++ b/vulkan/scripts/generator_common.py
@@ -22,7 +22,7 @@
 import xml.etree.ElementTree as element_tree
 
 # Extensions unsupported on Android.
-_BLACKLISTED_EXTENSIONS = [
+_BLOCKED_EXTENSIONS = [
     'VK_EXT_acquire_xlib_display',
     'VK_EXT_direct_mode_display',
     'VK_EXT_display_control',
@@ -192,7 +192,7 @@
   if cmd not in extension_dict:
     return True
   else:
-    if extension_dict[cmd] not in _BLACKLISTED_EXTENSIONS:
+    if extension_dict[cmd] not in _BLOCKED_EXTENSIONS:
       return True
   return False