[v3] testsuite consistency checks

[Benjamin Kosnik]

This fixes up the rest of the inconsistencies found when typing "make 
testsuite_files" and looking through the list of files in the libstdc++ 
testsuite.

Changes:
1) correct comment as pointed by Paolo
2) consistent file naming of explicit_instantiation.cc
3) move dr438 checks into class-being-tested requirements directory, as 
done with basic_string.

Sorry for the churn. We're starting to do pretty big transformations 
while testing and it helps if there is only one way to do things.

tested x86/linux

-benjamin
-------------- next part --------------
A non-text attachment was scrubbed...
Name: p.20070501-1.bz2
Type: application/x-bzip
Size: 1388 bytes
Desc: not available
URL: <http://gcc.gnu.org/pipermail/libstdc++/attachments/20070501/b37fcbf7/attachment.bin>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: p.20070501-2.bz2
Type: application/x-bzip
Size: 3418 bytes
Desc: not available
URL: <http://gcc.gnu.org/pipermail/libstdc++/attachments/20070501/b37fcbf7/attachment-0001.bin>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: p.20070501-3.bz2
Type: application/x-bzip
Size: 1836 bytes
Desc: not available
URL: <http://gcc.gnu.org/pipermail/libstdc++/attachments/20070501/b37fcbf7/attachment-0002.bin>