Revert "dalvik/libdex: Don't reduce optimization level to -O2"

This reverts commit 89af812d26b77d7a5385e1a134fd8a49cf183ed6.
Revert "dalvik/libdex: Change to -O2 if we're building with -O3"

This reverts commit f43f8862da98f6cbaebb135ed096e16bbb44c951.
Revert "dalvik: Fix compile failures with -DNDEBUG and gcc >= 4.6"

This reverts commit 75f0427e7883816883b4ccf1e80c6e17d10fbdf1.