texinfo 6.1 drops -arch in darwin build

[Jack Howarth]

When building texinfo 6.1 on x86_64-apple-darwin15, the following
correction is required...

--- tp/Texinfo/Convert/XSParagraph/configure.ac.orig 2016-03-05
12:31:24.000000000 -0500
+++ tp/Texinfo/Convert/XSParagraph/configure.ac 2016-03-05
12:31:46.000000000 -0500
@@ -42,7 +42,7 @@
           fetch_conf $1

           # Remove any flags that aren't -I or -D
-          conf_value=`echo $conf_value | sed -e 's/-@<:@^ID@:>@@<:@^ @:>@*//g'`
+          conf_value=`echo $conf_value | sed -e 's/-@<:@^aID@:>@@<:@^
@:>@*//g'`
           AC_MSG_RESULT([$conf_value])

           AC_SUBST([PERL_CONF_$1], [$conf_value])

to prevent the instances of '-arch i386 -arch x86_64' in the perl
compiler flags from being turned into 'i386 x86_64' and breaking the
compilation of XSParagraph.
        Jack