dalvik: Fix various compile failures with gcc 4.6

This fixes numerous compile errors with gcc 4.6, and combinations
of -DNDEBUG, -DLOG_NDEBUG resulting in variables being defined but
not used - resulting in a compiler warning (or build breakage
with -Werror).

Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>

dalvik: Fix aliasing violation

Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>

dalvik/libdex: Change to -O2 if we're building with -O3

This is a workaround for an apparent gcc bug.
https://bugs.launchpad.net/linaro-android/+bug/948255

Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>

dalvik: Fix build with ISO C++11

Fixes some confusion between jchar and the new char16_t

Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>