setup: include software and Verilog files

Broken on Python 3.5
error: can't copy 'misoc/software': doesn't exist or not a regular file

MANIFEST.in

@@ -0,0 +1,4 @@
+graft misoc/software
+graft misoc/cores/lm32/verilog/submodule
+graft misoc/cores/mor1kx/verilog
+include misoc/cores/mxcrg.v

setup.py

@@ -31,6 +31,7 @@ setup(
         "Programming Language :: Python",
     ],
     packages=find_packages(),
+    include_package_data=True,
     entry_points={
         "console_scripts": [
             "flterm=misoc.tools.flterm:main",