Add bit helper utility

- Add it to the base build (the first one in the hierarchy that includes
  the activity manager).
- Add tab completion commands to envsetup.sh

Test: . build/envsetup.sh ; make
Change-Id: Id24acaa0f17f198bda329016ff17170ad93624ec
diff --git a/target/product/base.mk b/target/product/base.mk
index 456715f..22eddf3 100644
--- a/target/product/base.mk
+++ b/target/product/base.mk
@@ -27,6 +27,7 @@
     app_process \
     applypatch \
     audioserver \
+    bit \
     blkid \
     bmgr \
     bugreport \