Make viewer compile on standalone linux x86_64

This involves making libllcommon shared, a change
that was not finished for windows/Mac.
More changes are needed to indra/newview/viewer_manifest.py
for those two operating systems, as well as to
indra/copy_win_scripts.

I did not test this on linux 32bit, nor non-standalone
on that OS, either.

I did not check voice (which will very likely not work
anyway on 64bit). And currently the webkit plugin doesn't
work for me, but I'll fix that in a different commit.

indra/media_plugins/webkit/CMakeLists.txt

@@ -27,6 +27,7 @@ include_directories(
     ${LLIMAGE_INCLUDE_DIRS}
     ${LLRENDER_INCLUDE_DIRS}
     ${LLWINDOW_INCLUDE_DIRS}
+    ${LLQTWEBKIT_INCLUDE_DIR}
 )