changes for additional packages to be packaged from the same build. see BuildParams for example environment variables used to specify the packages and their channels and sourceids. also updated mac packages to use a larger virtual drive and auto-open on download

Removing build.sh darwin symbols hack.  Adding '-g' to both CFLAGS and CXXFLAG to have cmake generation debug symbols in xcode.

Apparently the hack to get release and debug viewer builds into separate build configs means checking  in build.sh is useless. Fixed the conditional around uploading the symbolfile to check  instead, which seems to be the correct pattern.

WOLF-363: (partial) correct ordering of cleaning build dir vs running
          'autobuild install'

Fix for CHOP-619.  Found a general solution to our vs2010 precompiled headers problems and eliminated all our special cases for handling them.

viewer_manifest.py will now package a summary.json file, if present; but
previously build.sh didn't create that file until after the viewer build.

Patch taken from here: https://paste.lindenlab.com/show/6902/