As well as adding the necessary methods, a few other changes to the adb
remote:
* Use ".annextmp" extension for temp files, to avoid conflict with other
temp files.
* Stop using "echo $?" to get exit status of command inside adb.
There were two problems; first the "echo" just before it meant it was
always 0! And secondly, it seems kind of random on my phone whether it's
1 or 0, not dependant on whether the command seems to have succeeded.
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