Merge pull request #252 from jogarock/Xilinx

Xilinx FPGA bitstream

src/binwalk/magic/misc

@@ -79,3 +79,7 @@
 
 0       string      \x00\x53\x46\x48                                    OSX DMG image
 >0x38   string      !d\x00i\x00s\x00k\x00\x20\x00i\x00m\x00a\x00g\x00e  invalid{invalid)
+
+# Xilinx FPGA Bitstream
+# Ref: http://www.xilinx.com/support/answers/7891.html
+0       ubequad        0xffffffffaa995566  Xilinx Virtex/Spartan FPGA bitstream dummy + sync word