Kludge poptBadOption() to return something semi-meaningful on exec alias fail

- poptBadOption() is totally unaware of exec alias failures, and
  will return either the first argument or last option, giving
  wonderfully misleading error messages (#697435, #710267).
- Remember execvp() first argument on failure and return that
  from poptBadOption() if present to give the user a reasonable
  clue what exactly went wrong.

diff -up popt-1.13/popt.c.execfail popt-1.13/popt.c
--- popt-1.13/popt.c.execfail	2012-08-02 16:08:34.762315304 +0300
+++ popt-1.13/popt.c	2012-08-02 16:11:41.352683721 +0300
@@ -186,6 +186,7 @@ poptContext poptGetContext(const char *
     con->flags = flags;
     con->execs = NULL;
     con->numExecs = 0;
+    con->execFail = NULL;
     con->finalArgvAlloced = argc * 2;
     con->finalArgv = calloc( con->finalArgvAlloced, sizeof(*con->finalArgv) );
     con->execAbsolute = 1;
@@ -234,6 +235,7 @@ void poptResetContext(poptContext con)
     con->nextLeftover = 0;
     con->restLeftover = 0;
     con->doExec = NULL;
+    con->execFail = _free(con->execFail);
 
     if (con->finalArgv != NULL)
     for (i = 0; i < con->finalArgvCount; i++) {
@@ -468,6 +470,7 @@ if (_popt_debug)
 /*@-nullstate@*/
     rc = execvp(argv[0], (char *const *)argv);
 /*@=nullstate@*/
+    con->execFail = xstrdup(argv[0]);
 
 exit:
     if (argv) {
@@ -1194,11 +1197,19 @@ int poptAddItem(poptContext con, poptIte
 const char * poptBadOption(poptContext con, unsigned int flags)
 {
     struct optionStackEntry * os = NULL;
+    const char *badOpt = NULL;
 
-    if (con != NULL)
-	os = (flags & POPT_BADOPTION_NOALIAS) ? con->optionStack : con->os;
+    if (con != NULL) {
+	/* Stupid hack to return something semi-meaningful from exec failure */
+	if (con->execFail) {
+	    badOpt = con->execFail;
+	} else {
+	    os = (flags & POPT_BADOPTION_NOALIAS) ? con->optionStack : con->os;
+	    badOpt = os->argv[os->next - 1];
+	}
+    }
 
-    return (os != NULL && os->argv != NULL ? os->argv[os->next - 1] : NULL);
+    return badOpt;
 }
 
 const char * poptStrerror(const int error)
diff -up popt-1.13/poptint.h.execfail popt-1.13/poptint.h
--- popt-1.13/poptint.h.execfail	2012-08-02 16:08:34.000000000 +0300
+++ popt-1.13/poptint.h	2012-08-02 16:12:35.796500122 +0300
@@ -78,6 +78,7 @@ struct poptContext_s {
 /*@owned@*/ /*@null@*/
     poptItem execs;
     int numExecs;
+    char * execFail;
 /*@only@*/ /*@null@*/
     const char ** finalArgv;
     int finalArgvCount;