Compile on Freebsd (#1044)

* Compile on Freebsd

Small changes needed for compilation on Freebsd. Note that you'll have
to pass -DEQEMU_BUILD_ZLIB=OFF on the cmake command line. The bundled
zlib-ng does not build on Freebsd even though mainline zlib-ng does.

* Fix build errors: typo

common/crash.cpp

@@ -118,6 +118,11 @@ void set_exception_handler() {
 #include <unistd.h>
 #include <sys/fcntl.h>
 
+#ifdef __FreeBSD__
+#include <signal.h>
+#include <sys/stat.h>
+#endif
+
 void print_trace()
 {
 	auto uid = geteuid();