Maintenance Release: Input Fix & Enable Memory Card Removal

This small maintenance release makes the following changes:

• Input polling has been modified to fix glitches (e.g. double inputs) when using a DualShock controller in games such as Medal of Honor and Final Fantasy IX. Many thanks to @EhotPotaskun for PR'ing this improvement!

• The option to remove memory cards has been added (simply highlight the Memory card Slot* menu entry and press 'left' until the setting reads empty). Removal of the second memory card is required in order to run the game "Codename: Tenka". (Again, many thanks to @EhotPotaskun for making me aware of this issue, and for providing an initial implementation of the feature)

OpenDingux Beta: "Core settings" menu crash fix

This maintenance release fixes a nasty bug in the Core settings menu. This was being drawn at the wrong Y offset, such that the last entry (Restore defaults) was positioned off-screen - and as a result, an overflow of the screen buffer was occurring. While the issue was mostly hidden when using OpenDingux stock firmwares, OpenDingux Beta has more robust memory management - and the screen buffer overflow would generate a segfault (crash) when accessing the Core settings menu...

Now the Core settings menu is positioned correctly. The Restore defaults entry is accessible, and crashes on OpenDingux Beta no longer occur.

OpenDingux Beta Support

This release adds full OpenDingux beta (https://zcrc.me/) support. A new pcsx4all_rg350_odbeta.opk build is provided:

• This is compiled using the latest GCW0 toolchain, with huge-pages support (for improved performance)
• The (HW) Keep Aspect and (HW) Video Filter options now work correctly on OpenDingux Beta versions released after 16/03/2021

libchdr Update

This maintenance release updates libchdr to the latest upstream version (this is the library used for reading CHD disk images). The main benefit here is that the libflac dependency is replaced by dr_flac (https://mackron.github.io/dr_flac). This removes a vast of amount code (~50k sloc), and also reduces the performance overheads of FLAC decoding by ~15%.

Rumble Improvements

This minor update rewrites the rumble interface to improve the accuracy and response of haptic feedback effects. In addition, a new Core settings > Rumble Strength option allows the overall magnitude of the vibration to be adjusted.

CHD Support

This PR backports two features from https://github.com/libretro/pcsx_rearmed (many thanks to the original authors!)

• CHD support: The emulator is now compatible with compressed disk images in CHD format (https://en.wikipedia.org/wiki/MAME#Game_data)

• Optional asynchronous CD access: A new Core settings > CD Access option has been added. When set to Async, CD data is read in a background thread and prefetched when possible; in addition, a small memory cache is maintained for fast access to the last fetched data. This can reduce stuttering in games with frequent disk access

Quality of Life Improvements

This release for the RG350(M) - and related devices - is identical to tonyjih's fork, but with the following QoL enhancements:

• A new Core settings > Menu Toggle Combo option has been added. This allows the selection of a button combo that can be used (in addition to POWER) to open the menu while a game is running. Available combos are L3+R3 and SELECT+START.

• A new GPU settings > (HW) Keep Aspect option has been added. When using the hardware (IPU) scaler, this allows pixel aspect ratio scaling to be enabled/disabled.

• A new GPU settings > (HW) Video Filter option has been added. When using the hardware (IPU) scaler, this allows selection of the image filtering method from one of: bicubic (default), bilinear or nearest.

• Optional per-disk memory cards are now supported. Setting Memory card Slot1/2 to the lowest value will create memory cards named after the disk serial number. When swapping CDs, any per-disk memory cards will be swapped out to match the new serial unless a multi-disk .pbp is being used (where it's one set of memory cards per .pbp file).

• Configuration overrides are now supported. Selecting Config Override from the main menu will save the current settings into a disk-specific config file, which will thereafter be used instead of the default when loading/exiting the game.