Fixes #17.

If you edit a zip file with Windows Explorer, it will rewrite the entire
central directory, setting all files version_needed field to 2.0/MS-DOS,
but it won't touch files that it doesn't plan to alter, so you might end
up with a local header that doesn't match the central directory details.

We aren't currently using the version_needed information, so now we just
favor the local header's copy of it in case we ever need it, and don't
complain if the central directory doesn't match.

Fixes #24.

Fixes #4.

…adai!).

Fixes #3.

(and several more probably _should_ be but I don't have the details on
them at the moment. But now it's just changing a 1 to a 0 to fix those!)

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.