Add xdg mime support on Linux.

base/third_party/xdg_mime/compile.patch

Index: base/third_party/xdg_mime/compile.patch
===================================================================
--- base/third_party/xdg_mime/compile.patch	(revision 0)
+++ base/third_party/xdg_mime/compile.patch	(revision 0)
@@ -0,0 +1,27 @@
+--- a/xdgmimecache.c
++++ b/xdgmimecache.c
+@@ -40,6 +40,8 @@
+ 
+ #include <netinet/in.h> /* for ntohl/ntohs */
+ 
++#define HAVE_MMAP 1
++
+ #ifdef HAVE_MMAP
+ #include <sys/mman.h>
+ #else
+@@ -1000,5 +1002,3 @@
+ 	    dump_glob_node (cache, offset + 20 * j, 0);
+   }
+ }
+-
+-
+--- a/xdgmimeglob.c
++++ b/xdgmimeglob.c
+@@ -375,7 +375,6 @@
+   int i, n;
+   MimeWeight mimes[10];
+   int n_mimes = 10;
+-  xdg_unichar_t *ucs4;
+   int len;
+ 
+   /* First, check the literals */