FastCGI: Improve handling of EPIPE while writing response

That would previously result in the worker getting killed with SIGPIPE.
Which works, but we can also recover from that error without restarting
the process.

FU.xs

@@ -3,7 +3,7 @@
 #include <time.h> /* struct timespec & clock_gettime() */
 #include <string.h> /* strerror() */
 #include <arpa/inet.h> /* inet_ntop(), inet_ntoa() */
-#include <sys/socket.h> /* fd passing */
+#include <sys/socket.h> /* send(), fd passing */
 #include <sys/un.h> /* fd passing */
 #include <dlfcn.h> /* dlopen() etc */
 
@@ -170,11 +170,11 @@ void print(fufcgi *ctx, SV *sv)
   CODE:
     STRLEN len;
     const char *buf = SvPVbyte(sv, len);
-    fufcgi_print(ctx, buf, len);
+    fufcgi_print(aTHX_ ctx, buf, len);
 
 void flush(fufcgi *ctx)
   CODE:
-    fufcgi_done(ctx);
+    fufcgi_done(aTHX_ ctx);
 
 void DESTROY(fufcgi *ctx)
   CODE: