Fix sigpipe handler

CUPS manual recommends to ignore SIGPIPE signal in filters (since when
they're in chain, children may stop and such signal will disturb others)
We are not intended to be used in chain, however let's follow
the recommendation.

rastertozj.c

@@ -208,7 +208,7 @@ typedef void (*__sighandler_t)(int);
 
 __sighandler_t old_signal;
 void finishPage() {
-  signal(15, old_signal);
+  signal(SIGTERM, old_signal);
 }
 
 // sent on job canceling
@@ -220,7 +220,7 @@ void cancelJob() {
 }
 
 // invoked before starting to print a page
-void startPage() { old_signal = signal(15, cancelJob); }
+void startPage() { old_signal = signal(SIGTERM, cancelJob); }
 
 void DebugPrintHeader (cups_page_header2_t* pHeader)
 {
@@ -387,6 +387,9 @@ static inline void send_raster(const unsigned char *pBuf, int width8,
 //////////////////////////////////////////////
 //////////////////////////////////////////////
 int main(int argc, char *argv[]) {
+
+  signal(SIGPIPE, SIG_IGN);
+
   if (argc < 6 || argc > 7) {
     fputs("ERROR: rastertozj job-id user title copies options [file]\n",
           stderr);