fix exit status: several executables reported success (0) on failure or vice versa

Two bug patterns fixed across src/*.cpp:

- musrfit, musrview, any2many, addRun, musrFT, musrt0: a local
  success/ok/isGood flag was tracked and an error printed, but the
  function fell through to an unconditional `return PMUSR_SUCCESS;`
  at the end instead of propagating the failure.
- msr2data, msr2msr: the success path returned a nonzero code (1)
  instead of 0.

Also propagate previously-ignored return codes to the process exit
status in dump_header (format-dispatch functions), musrRootValidation
(schema validation / consistency checks), and write_musrRoot_runHeader
(FillFolder failure).

src/dump_header.cpp

@@ -1083,21 +1083,23 @@ int main(int argc, char *argv[])
 
   boost::to_lower(fileFormat);
 
+  int status = 0;
   if (boost::iequals(fileFormat, "MusrRoot") || boost::iequals(fileFormat, "ROOT")) {
-    dump_header_root(pathFln, summary, counts);
+    status = dump_header_root(pathFln, summary, counts);
   } else if (boost::iequals(fileFormat, "NeXus")) {
 #ifdef PNEXUS_ENABLED
-    dump_header_nexus(pathFln, counts);
+    status = dump_header_nexus(pathFln, counts);
 #else
     std::cout << std::endl << "Sorry, NeXus is not enabled, hence I cannot help you." << std::endl;
+    status = 1;
 #endif
   } else if (boost::iequals(fileFormat, "PSI-BIN") || boost::iequals(fileFormat, "PSI-MDU")) {
-    dump_header_psi_bin(pathFln, fileFormat, counts);
+    status = dump_header_psi_bin(pathFln, fileFormat, counts);
   } else if (boost::iequals(fileFormat, "MUD")) {
-    dump_header_mud(pathFln, counts);
+    status = dump_header_mud(pathFln, counts);
   } else if (boost::iequals(fileFormat, "WKM")) {
-    dump_header_wkm(pathFln);
+    status = dump_header_wkm(pathFln);
   }
 
-  return 0;
+  return status;
 }