Rewrite of "--remote", to use a temporary file for information exchange instead of a SysV IPC message queue, to correct the fault where "make check -j32" would fail due to every PV exit removing the message queue.

src/include/pv-internal.h

@@ -142,6 +142,10 @@ struct pvstate_s {
 	volatile sig_atomic_t pv_sig_newsize;	 /* whether we need to get term size again */
 	volatile sig_atomic_t pv_sig_abort;	 /* whether we need to abort right now */
 	volatile sig_atomic_t reparse_display;	 /* whether to re-check format string */
+#ifdef SA_SIGINFO
+	volatile sig_atomic_t pv_sig_rxusr2;	 /* whether SIGUSR2 was received */
+	volatile pid_t pv_sig_sender;		 /* PID of sending process for SIGUSR2 */
+#endif
 	struct sigaction pv_sig_old_sigpipe;
 	struct sigaction pv_sig_old_sigttou;
 	struct sigaction pv_sig_old_sigtstp;
@@ -150,6 +154,9 @@ struct pvstate_s {
 	struct sigaction pv_sig_old_sigint;
 	struct sigaction pv_sig_old_sighup;
 	struct sigaction pv_sig_old_sigterm;
+#ifdef SA_SIGINFO
+	struct sigaction pv_sig_old_sigusr2;
+#endif
 
 	/*****************
 	 * Display state *

src/include/pv.h

@@ -15,6 +15,7 @@
 
 #include <stdlib.h>
 #include <stdbool.h>
+#include <signal.h>
 #include <time.h>
 #include <sys/types.h>
 
@@ -200,6 +201,13 @@ extern off_t pv_calc_total_size(pvstate_t);
  */
 extern void pv_sig_init(pvstate_t);
 
+#ifdef SA_SIGINFO
+/*
+ * Return true if SIGUSR2 has been received, and indicate the sender.
+ */
+extern bool pv_sigusr2_received(pvstate_t, pid_t *);
+#endif
+
 /*
  * Enter the main transfer loop, transferring all input files to the output.
  */