Check $DECODED_ARGS for ReverseTxns URL parameter

Various pages that show the reverse history order option do not actually
respect the ReverseTxns parameter when passed in.

Updating ShowHistoryHeader and ShowHistoryPage to check for ReverseTxns
in DECODED_ARGS fixes these pages without having to fix them all
individually.

share/html/Elements/ShowHistoryHeader

@@ -58,7 +58,7 @@ $Title             => loc('History')
 my $record_type = $Object->RecordType;
 my $histid      = "\L$record_type\E-" . $Object->id . "-history";
 
-my $reverse_txns = $ARGS{'ReverseTxns'};
+my $reverse_txns = $ARGS{'ReverseTxns'} || $DECODED_ARGS->{ReverseTxns};
 if ( $reverse_txns ) {
     # If we got something, reverse it for the link
     $reverse_txns = $reverse_txns eq 'ASC' ? 'DESC' : 'ASC';

share/html/Elements/ShowHistoryPage

@@ -59,6 +59,7 @@ $PathPrefix        => ''
 my $trans_content = {};
 my $trans_attachments = {};
 
+$ARGS{'ReverseTxns'} ||= $DECODED_ARGS->{ReverseTxns};
 if ( $ARGS{'ReverseTxns'} ) {
     $Transactions = $Object->SortedTransactions($ARGS{'ReverseTxns'});
 }