android: bug fix for OutOfMemeoryError while loading slideshow, handle exception. reported in PlayStore.

VBOX: When running a 32-bit vboxwrapper on a 64-bit Windows machine, exit with a temporary error suggesting that the volunteer upgrade to a 64-bit BOINC client.  32-bit vboxwrapper cannot detect VirtualBox on a 64-bit system.

client and manager: the set_cc_config and get_cc_config GUI RPCs had nonstandard replies, which weren't parsed correctly by the calling code.

The reply from a GUI RPC that don't return info is one of:
<success/>
<error>error message</error>
<status>N</status>

Wrapper (Android): don't get the CPU time of tasks.  The function sometimes crashes (under investigation), and the GUI doesn't show CPU time anyway.

scales that cause it to fail. That prevents host_app_version PFCs not to be
updated for perfectly reasonable credit claims.  Since there is a max credit
granted this mechanism is unneccesary, anyway.

scheduler: sample code for the SSE3 plan class must check for "pni" rather than "sse3"; clients report "pni"

Many Android users had existing preferences with settings like
"don't compute when idle" that make sense for PCs but not mobile devices.
When this pref is enforced on Android, no computing happens
and user confusion results.
We're addressing this by using only local prefs on Android.
We considered other approaches - e.g. having a "mobile" venue -
but they're too complex.

client (Android): allow GUI to pass MAC address to client via set_host_info().  If domain name is "localhost" and MAC address is nonempty, use MAC address instead of domain name when showing host on project web page.

WINBUILD: Re-enable the custom actions which modify the VirtualBox.VirtualBox permissions so that boinc_project can launch VMs.

MGR: On Linux, initialize exclusive apps dialog to start from directory "/usr/bin/" instead of from "/" (from Toralf Förster)

Trying to fix bug where timer thread stops doing anything
after first suspend on Android (old, 1-core devices).
I suspect that the sleep() in the worker thread's signal handle
is sleeping the entire process.
Insert a sched_yield() before the sleep so that the time thread will run.