Add support for absolute/relative imports and if/else expressions:
 - regenerate ast.py
 - add future flags for absolute-import and with-statement so they
   (hopefully) properly get set in code-object flags
 - try out if/else expressions in actual code for the hell of it.

Seems to generate the same kind of bytecode as the normal compiler.
diff --git a/Lib/compiler/consts.py b/Lib/compiler/consts.py
index a6cf559..d760982 100644
--- a/Lib/compiler/consts.py
+++ b/Lib/compiler/consts.py
@@ -17,3 +17,5 @@
 CO_GENERATOR = 0x0020
 CO_GENERATOR_ALLOWED = 0x1000
 CO_FUTURE_DIVISION = 0x2000
+CO_FUTURE_ABSIMPORT = 0x4000
+CO_FUTURE_WITH_STATEMENT = 0x8000