Fix PHYSFS deprecation warnings

[slime73]

Original report by Martin Felis (Bitbucket: MartinFelis, GitHub: MartinFelis).

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Various warnings of PHYSFS are generated such as:

jni/love/src/modules/filesystem/physfs/Filesystem.cpp:504:59: warning: 'const char* PHYSFS_getUserDir()' is deprecated (declared at jni/love/../physfs-2.1.0/src/physfs.h:797) [-Wdeprecated-declarations]

Nothing critical, but would be nicer.

[slime73]

Original comment by Alex Szpakowski (Bitbucket: slime73, GitHub: slime73).

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I've fixed most of these in a recent commit, but not PHYSFS_getUserDir because it's deprecated without a replacement (in PhysFS at least.)

[slime73]

Original comment by Martin Felis (Bitbucket: MartinFelis, GitHub: MartinFelis).

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Thanks!