Fix `make distcheck`.
Fix `make distcheck`.

	* Makefile.am: Fix `make distcheck`; it was broken once AssemblyInfo.cs was
	  made into a generated file.

MikeJansen/NDesk.Options.StrongNamed,MikeJansen/NDesk.Options.StrongNamed,chakrit/ndesk-options-mirror,chakrit/ndesk-options-mirror,MikeJansen/NDesk.Options.StrongNamed