Powerpoint tests: test raw openxml

Output files confirmed not to be corrupt, and with content as
expected, on PowerPoint 2013 on Windows 10 (virtualbox on linux).

test/Tests/Writers/Powerpoint.hs

@@ -95,5 +95,8 @@ tests = groupPptxTests [ pptxTests "Inline formatting"
                          def
                          "pptx/remove_empty_slides.native"
                          "pptx/remove_empty_slides.pptx"
-
+                       , pptxTests "raw ooxml"
+                         def
+                         "pptx/raw_ooxml.native"
+                         "pptx/raw_ooxml.pptx"
                        ]

test/pptx/raw_ooxml.native

@@ -0,0 +1,3 @@
+[Para [Str "Here",Space,Str "is",Space,Str "some",Space,Str "text,",Space,Str "written",Space,Str "as",Space,Str "a",Space,Str "raw",Space,Str "inline:",Space,RawInline (Format "openxml") "<a:r><a:rPr /><a:t>Here are examples of </a:t></a:r><a:r><a:rPr i=\"1\" /><a:t>italics</a:t></a:r><a:r><a:rPr /><a:t>, </a:t></a:r><a:r><a:rPr b=\"1\" /><a:t>bold</a:t></a:r>"]
+,HorizontalRule
+,RawBlock (Format "openxml") "      <p:sp>\n        <p:nvSpPr>\n          <p:cNvPr id=\"3\" name=\"Content Placeholder 2\"/>\n          <p:cNvSpPr>\n            <a:spLocks noGrp=\"1\"/>\n          </p:cNvSpPr>\n          <p:nvPr>\n            <p:ph idx=\"1\"/>\n          </p:nvPr>\n        </p:nvSpPr>\n        <p:spPr/>\n        <p:txBody>\n          <a:bodyPr/>\n          <a:lstStyle/>\n          <a:p>\n            <a:pPr lvl=\"1\"/>\n            <a:r>\n              <a:rPr/>\n              <a:t>Bulleted bulleted lists.</a:t>\n            </a:r>\n          </a:p>\n          <a:p>\n            <a:pPr lvl=\"1\"/>\n            <a:r>\n              <a:rPr/>\n              <a:t>And go to arbitrary depth.</a:t>\n            </a:r>\n          </a:p>\n          <a:p>\n            <a:pPr lvl=\"2\"/>\n            <a:r>\n              <a:rPr/>\n              <a:t>Like this</a:t>\n            </a:r>\n          </a:p>\n          <a:p>\n            <a:pPr lvl=\"3\"/>\n            <a:r>\n              <a:rPr/>\n              <a:t>Or this</a:t>\n            </a:r>\n          </a:p>\n          <a:p>\n            <a:pPr lvl=\"2\"/>\n            <a:r>\n              <a:rPr/>\n              <a:t>Back to here.</a:t>\n            </a:r>\n          </a:p>\n        </p:txBody>\n      </p:sp>"]