libstdc++: Stop copying all data files into test directory

This removes the TODO in libstdc++_init, so that we don't copy all *.tst
and *.txt files from testsuite/data into every test's working directory.
Instead, only the necessary files declared with dg-additional-files are
copied.

libstdc++-v3/ChangeLog:

	* testsuite/lib/libstdc++.exp (libstdc++_init): Do not copy all
	data files into test directory.

libstdc++-v3/testsuite/lib/libstdc++.exp

@@ -158,11 +158,6 @@ proc libstdc++_init { testfile } {
     global dg-do-what-default
     set dg-do-what-default run
 
-    # Copy all required data files.
-    # TODO: Use dg-additional-files in individual tests instead of doing this.
-    v3-copy-files [glob -nocomplain "$srcdir/data/*.tst"]
-    v3-copy-files [glob -nocomplain "$srcdir/data/*.txt"]
-
     set ld_library_path_tmp ""
 
     # Locate libgcc.a so we don't need to account for different values of