Fix configure script datadir/datarootdir definition.

Author: michaelrsweet

configure

@@ -5584,7 +5584,7 @@ then :
 
 else $as_nop
 
-	datarootdir="$prefix/share"
+	datarootdir="$realprefix/share"
 
 fi
 
@@ -5600,7 +5600,7 @@ then :
 
 else $as_nop
 
-	datadir="$prefix/share"
+	datadir="$realprefix/share"
 
 fi
 
@@ -5643,7 +5643,7 @@ fi
 
 else $as_nop
 
-	sysconfdir="$prefix/etc"
+	sysconfdir="$realprefix/etc"
 
 fi
 

configure.ac

@@ -619,15 +619,15 @@ AS_IF([test "$datarootdir" = "\${prefix}/share"], [
     AS_IF([test "$prefix" = "/"], [
 	datarootdir="/usr/share"
     ], [
-	datarootdir="$prefix/share"
+	datarootdir="$realprefix/share"
     ])
 ])
 
 AS_IF([test "$datadir" = "\${prefix}/share"], [
     AS_IF([test "$prefix" = "/"], [
 	datadir="/usr/share"
     ], [
-	datadir="$prefix/share"
+	datadir="$realprefix/share"
     ])
 ], [test "$datadir" = "\${datarootdir}"], [
     datadir="$datarootdir"
@@ -648,7 +648,7 @@ AS_IF([test "$sysconfdir" = "\${prefix}/etc"], [
 	    sysconfdir="/etc"
 	])
     ], [
-	sysconfdir="$prefix/etc"
+	sysconfdir="$realprefix/etc"
     ])
 ])