libcxx: Rename .hpp files in libcxx/test/support to .h

LLVM uses .h as its extension for header files.

Files renamed using:

    for f in libcxx/test/support/*.hpp; do git mv $f ${f%.hpp}.h; done

References to the files updated using:

    for f in $(git diff master | grep 'rename from' | cut -f 3 -d ' '); do
        a=$(basename $f);
        echo $a;
        rg -l $a libcxx | xargs sed -i '' "s/$a/${a%.hpp}.h/";
    done

HPP include guards updated manually using:

    for f in $(git diff master | grep 'rename from' | cut -f 3 -d ' '); do
      echo ${f%.hpp}.h ;
    done | xargs mvim

Differential Revision: https://reviews.llvm.org/D66104

llvm-svn: 369481
diff --git a/libcxx/test/std/utilities/optional/optional.object/triviality.pass.cpp b/libcxx/test/std/utilities/optional/optional.object/triviality.pass.cpp
index 3af60a6..1aff9df 100644
--- a/libcxx/test/std/utilities/optional/optional.object/triviality.pass.cpp
+++ b/libcxx/test/std/utilities/optional/optional.object/triviality.pass.cpp
@@ -22,7 +22,7 @@
 #include <optional>
 #include <type_traits>
 
-#include "archetypes.hpp"
+#include "archetypes.h"
 
 #include "test_macros.h"