Add sample profiling interface to startMethodTracing.

Frameworks base side of this change. Also changed art and libcore.

Change-Id: Ib5ba0445163dca714d1ae66430750346ff8811be
Don't rely on gcc extensions

Variable-length arrays of non-POD data types are a gcc extension
not currently supported by clang.

Change-Id: I9cd1aed742ac70e642771ff455582727fbafaec2
Signed-off-by: Bernhard Rosenkränzer <Bernhard.Rosenkranzer@linaro.org>