osdep/io: add android related bullshit

This fixes >2GiB files with at least API level 21.
See: https://android.googlesource.com/platform/bionic/+/master/docs/32-bit-abi.md
for the gritty details.

* Based on libavformat's things, except we do not care about API
  versions or NDKs without unistd.h, which contains all sorts of
  things that we utilize.
* Redefines lseek to always point to the 64bit version.
* Redefines fseeko to always point towards an inlined static
  implementation that utilizes the 64bit version of lseek underneath.

osdep/io.h

@@ -32,6 +32,33 @@
 #include <glob.h>
 #endif
 
+#ifdef __ANDROID__
+#  include <unistd.h>
+#  include <stdio.h>
+
+// replace lseek with the 64bit variant
+#ifdef lseek
+#  undef lseek
+#endif
+#define lseek(f,p,w) lseek64((f), (p), (w))
+
+// replace possible fseeko with a
+// lseek64 based solution.
+#ifdef fseeko
+#  undef fseeko
+#endif
+static inline int mp_fseeko(FILE* fp, off64_t offset, int whence) {
+    int ret = -1;
+    if ((ret = fflush(fp)) != 0) {
+        return ret;
+    }
+
+    return lseek64(fileno(fp), offset, whence) >= 0 ? 0 : -1;
+}
+#define fseeko(f,p,w) mp_fseeko((f), (p), (w))
+
+#endif // __ANDROID__
+
 #ifndef O_BINARY
 #define O_BINARY 0
 #endif