Closes #15 .

not libphysfs, because of os2 limitation.

Copy and pasted from SDL a little too quickly.  :)

…found

Apparently use of LIB_SUFFIX is now discouraged. GNUInstallDirs does a
better job of setting a default.

The libdir of ${prefix}/lib in the pkg-config file caused warnings,
and possibly even failures, when linking on multilib systems where
/usr/lib is for 32-bit libraries rather than 64-bit libraries.

…ion.

Co-authored-by: Victor Romero <romerosanchezv@gmail.com>

This compiled and worked on Android before, if you didn't care about
PHYSFS_getBaseDir() and PHYSFS_getPrefDir() being useful. Now you can pass
PHYSFS_init() some necessary Android objects to solve this. Passing NULL
to PHYSFS_init is acceptable and will simply report "/" for the base dir and
prefdir, under the assumption that the app queried the OS for these directly
instead.

This was clearly copied from a previous line but wasn't updated with the
correct condition to check, so if malloc() failed, it would dereference NULL
instead of reporting an error.