biology/blat: Fix build on DF (taken from dports)

svn path=/head/; revision=428834

biology/blat/files/patch-lib_fof.c

@@ -0,0 +1,14 @@
+--- lib/fof.c.orig	2014-11-06 03:15:59 UTC
++++ lib/fof.c
+@@ -336,7 +336,11 @@ static int cmpOnFilePos(const void *va, 
+ {
+ const struct fofBatch *a = *((struct fofBatch **)va);
+ const struct fofBatch *b = *((struct fofBatch **)vb);
++#ifdef __DragonFly__
++int dif = (struct __FILE_public*)a->f - (struct __FILE_public*)b->f;
++#else
+ int dif = a->f - b->f;
++#endif
+ if (dif == 0)
+     dif = a->offset - b->offset;
+ return dif;