Libretro updates

[sonninnos]

• Adjusted av_info so that timing matches the actual rate audio is pushed, since it is never exact 60 even in VGA mode but the usual NTSC 59.94 instead, and 240p NTSC is not 59.94 either, but ~59.82, which is pretty common for that resolution in other hardware too
  • Measured and confirmed by extensive logging and audio buffer statistics observation. 240pSuite and Gunlord are good test cases
  • Also made sure there are no duplicate av_info spamming and reinits on startup and no extra max size change reinits
• Prevent audio muting on fast-forward so that the frontend option can decide
• Allow CHD launching of .hidden-chd for example instead of strict .chd