std-ddox: Define REF1 macro variants

Fixup for dlang#1802 and dlang/phobos#5554.

Author: CyberShadow

std-ddox.ddoc

@@ -5,9 +5,12 @@ _=
 
 REF_HELPER=$2$(DOT_PREFIXED_SKIP $+).$1
 REF=$(D $(REF_HELPER $1, $+))
+REF1=$(D $2.$1)
 REF_ALTTEXT=$(DDOX_NAMED_REF $(REF_HELPER $+), $1)
+REF1_ALTTEXT=$(D $3.$2, $1)
 MREF_HELPER=$1$(DOT_PREFIXED $+)
 MREF=$(D $(MREF_HELPER $1, $+))
 MREF_ALTTEXT=$(DDOX_NAMED_REF $(MREF_HELPER $+), $1)
+MREF1=$(D $1)
 DDOX_UNITTEST_HEADER=<span class="dlang_runnable"></span>
 _=