Perf tweaks to compiling and oat writing.

Make hot quick compiler routines inlinable.
Remove computation/use of SSA strings.
Use vector insert when writing to the end of a vector in the output stream, to
avoid a memset followed by a memcpy.

Generating boot.oat/art these changes improve performance by around 2.5%.

Change-Id: I3d0bdb01333efe8f0eda4bdf97225e0b307f934d