diff -Naur insight-6.8.orig/gdb/acinclude.m4 insight-6.8.new/gdb/acinclude.m4
--- insight-6.8.orig/gdb/acinclude.m4	2007-03-30 14:57:42.000000000 +0200
+++ insight-6.8.new/gdb/acinclude.m4	2008-10-09 19:40:56.000000000 +0200
@@ -96,8 +96,11 @@
   for i in \
 		`ls -dr /usr/local/src/tcl[[7-9]]* 2>/dev/null` \
 		`ls -dr /usr/local/lib/tcl[[7-9]]* 2>/dev/null` \
+		`ls -dr /usr/local/lib64/tcl[[7-9]]* 2>/dev/null` \
 		/usr/local/src/tcl \
 		/usr/local/lib/tcl \
+		/usr/local/lib64/tcl \
+		${includedir} \
 		${prefix}/include ; do
     if test -f $i/generic/tclInt.h ; then
       ac_cv_c_tclh=`(cd $i/generic; pwd)`
@@ -171,7 +174,8 @@
   fi
   # check in a few common install locations
   if test x"${ac_cv_c_tclconfig}" = x ; then
-    for i in `ls -d ${prefix}/lib /usr/local/lib 2>/dev/null` ; do
+    for i in `ls -d ${libdir} ${prefix}/lib ${prefix}/lib64 \
+     /usr/local/lib /usr/local/lib64 2>/dev/null` ; do
       if test -f "$i/tclConfig.sh" ; then
         ac_cv_c_tclconfig=`(cd $i; pwd)`
 	break
@@ -319,8 +323,11 @@
   for i in \
 		`ls -dr /usr/local/src/tk[[4-9]]* 2>/dev/null` \
 		`ls -dr /usr/local/lib/tk[[4-9]]* 2>/dev/null` \
+		`ls -dr /usr/local/lib64/tk[[4-9]]* 2>/dev/null` \
 		/usr/local/src/tk \
 		/usr/local/lib/tk \
+		/usr/local/lib64/tk \
+		${includedir} \
 		${prefix}/include ; do
     if test -f $i/generic/tk.h ; then
       ac_cv_c_tkh=`(cd $i/generic; pwd)`
@@ -394,7 +401,8 @@
   fi
   # check in a few common install locations
   if test x"${ac_cv_c_tkconfig}" = x ; then
-    for i in `ls -d ${prefix}/lib /usr/local/lib 2>/dev/null` ; do
+    for i in `ls -d ${libdir} ${prefix}/lib ${prefix}/lib64 \
+     /usr/local/lib /usr/local/lib64 2>/dev/null` ; do
       if test -f "$i/tkConfig.sh" ; then
         ac_cv_c_tkconfig=`(cd $i; pwd)`
 	break
@@ -499,7 +507,8 @@
   fi
   # check in a few common install locations
   if test x"${ac_cv_c_itclconfig}" = x ; then
-    for i in `ls -d ${prefix}/lib /usr/local/lib 2>/dev/null` ; do
+    for i in `ls -d ${libdir} ${prefix}/lib ${prefix}/lib64 \
+     /usr/local/lib /usr/local/lib64 2>/dev/null` ; do
       if test -f "$i/itclConfig.sh" ; then
         ac_cv_c_itclconfig=`(cd $i; pwd)`
 	break
@@ -625,7 +634,8 @@
   fi
   # check in a few common install locations
   if test x"${ac_cv_c_itkconfig}" = x ; then
-    for i in `ls -d ${prefix}/lib /usr/local/lib 2>/dev/null` ; do
+    for i in `ls -d ${libdir} ${prefix}/lib ${prefix}/lib64 \
+     /usr/local/lib /usr/local/lib64 2>/dev/null` ; do
       if test -f "$i/itkConfig.sh" ; then
         ac_cv_c_itkconfig=`(cd $i; pwd)`
 	break
@@ -827,10 +837,11 @@
   dnl those with the standalone portable GNU libiconv installed).
 
   AC_ARG_WITH([libiconv-prefix],
-[  --with-libiconv-prefix=DIR  search for libiconv in DIR/include and DIR/lib], [
+[  --with-libiconv-prefix=DIR  search for libiconv in DIR/{include, lib, lib64}], [
     for dir in `echo "$withval" | tr : ' '`; do
       if test -d $dir/include; then CPPFLAGS="$CPPFLAGS -I$dir/include"; fi
       if test -d $dir/lib; then LDFLAGS="$LDFLAGS -L$dir/lib"; fi
+      if test -d $dir/lib64; then LDFLAGS="$LDFLAGS -L$dir/lib64"; fi
     done
    ])