Add -h and -help for c_rehash script and app

Resolves GH1515 and GH1509.
Reviewed-by: NMatt Caswell <matt@openssl.org>

apps/rehash.c

@@ -403,6 +403,7 @@ OPTIONS rehash_options[] = {
     {OPT_HELP_STR, 1, '-', "Usage: %s [options] [cert-directory...]\n"},
     {OPT_HELP_STR, 1, '-', "Valid options are:\n"},
     {"help", OPT_HELP, '-', "Display this summary"},
+    {"h", OPT_HELP, '-', "Display this summary"},
     {"compat", OPT_COMPAT, '-', "Create both new- and old-style hash links"},
     {"old", OPT_OLD, '-', "Use old-style hash to generate links"},
     {"n", OPT_N, '-', "Do not remove existing links"},

doc/apps/rehash.pod

@@ -11,6 +11,7 @@ c_rehash, rehash - Create symbolic links to files named by the hash values
 
 B<openssl>
 B<rehash>
+B<[-h]>
 B<[-help]>
 B<[-old]>
 B<[-n]>
@@ -82,7 +83,7 @@ optionally prefixed with some text and an equals sign.
 
 =over 4
 
-=item B<-help>
+=item B<-help> B<-h>
 
 Display a brief usage message.
 

tools/c_rehash.in

@@ -30,7 +30,7 @@ while ( $ARGV[0] =~ /^-/ ) {
     if ( $flag eq '-old') {
 	    $x509hash = "-subject_hash_old";
 	    $crlhash = "-hash_old";
-    } elsif ( $flag eq '-h') {
+    } elsif ( $flag eq '-h' || $flag eq '-help' ) {
 	    help();
     } elsif ( $flag eq '-n' ) {
 	    $removelinks = 0;
@@ -38,15 +38,15 @@ while ( $ARGV[0] =~ /^-/ ) {
 	    $verbose++;
     }
     else {
-	    print STDERR "Usage error; try -help.\n";
+	    print STDERR "Usage error; try -h.\n";
 	    exit 1;
     }
 }
 
 sub help {
-	print "Usage: c_rehash [-old] [-h] [-v] [dirs...]\n";
+	print "Usage: c_rehash [-old] [-h] [-help] [-v] [dirs...]\n";
 	print "   -old use old-style digest\n";
-	print "   -h print this help text\n";
+	print "   -h or -help print this help text\n";
 	print "   -v print files removed and linked\n";
 	exit 0;
 }