patch 8.2.4686: configure doesn't find the Motif library with Cygwin

Problem:    Configure doesn't find the Motif library with Cygwin.
Solution:   Check for libXm.dll.a. (Kelvin Lee, closes #10077)
diff --git a/src/auto/configure b/src/auto/configure
index a5497d8..8ed46c8 100755
--- a/src/auto/configure
+++ b/src/auto/configure
@@ -10212,12 +10212,12 @@
 
         GUI_LIB_LOC="`echo $GUI_LIB_LOC|sed 's%-L%%g'`"
 
-            { $as_echo "$as_me:${as_lineno-$LINENO}: checking for location of Motif GUI libs" >&5
+                { $as_echo "$as_me:${as_lineno-$LINENO}: checking for location of Motif GUI libs" >&5
 $as_echo_n "checking for location of Motif GUI libs... " >&6; }
     gui_libs="`echo $x_libraries|sed 's%/^/^/*$%%'` `echo "$gui_XXX" | sed s/XXX/lib/g` /usr/lib/i386-linux-gnu /usr/lib/x86_64-linux-gnu `echo "$GUI_INC_LOC" | sed s/include/lib/` $GUI_LIB_LOC"
     GUI_LIB_LOC=
     for try in $gui_libs; do
-      for libtry in "$try"/libXm.a "$try"/libXm.so* "$try"/libXm.sl "$try"/libXm.dylib; do
+      for libtry in "$try"/libXm.a "$try"/libXm.dll.a "$try"/libXm.so* "$try"/libXm.sl "$try"/libXm.dylib; do
 	if test -f "$libtry"; then
 	  GUI_LIB_LOC=$try
 	fi