* mu-store.cc: add include unistd.h; this is needed by g++ 4.7 (as noted by

Tom Willemsen)

src/mu-store.cc

@@ -26,6 +26,7 @@
 #include <xapian.h>
 #include <cstring>
 #include <stdexcept>
+#include <unistd.h>
 
 #include <errno.h>