add sound modules to base linux.config; refactor such that all platforms
inherit from the base platform
[c64] add ARCADE to embedded SDL ifdef
Squashed 'tools/tinyalsa/' content from commit 782bfda

git-subtree-dir: tools/tinyalsa
git-subtree-split: 782bfda5e796cb46d0e7be0dc882ff686d5ad2a2
Merge commit 'be287f738ab9bac3f0164be1928bee23bf101891' as 'tools/tinyalsa'
[buildroot] patches to fix buildroot setup
bootup splash screen and startup sound