Revert "Update to Fuse 1.6.0 and libspectrum 1.5.0"

[inactive123]

Reverts libretro/fuse-libretro#89

[lgtm-com[bot]]

This pull request introduces 19 alerts and fixes 11 when merging 67ebf22ddafb7f6e60836816b5c2c24550273ff7 into f3ac46b5df6b6c62fc9b1c6b2760da7cfcb5fb58 - view on LGTM.com

new alerts:

• 6 for Expression has no effect
• 5 for FIXME comment
• 4 for Pointer overflow check
• 2 for Local variable hides global variable
• 1 for Unsigned comparison to zero
• 1 for Multiplication result converted to larger type

fixed alerts:

• 8 for FIXME comment
• 2 for Local variable hides global variable
• 1 for Expression has no effect