Simplify PDFWriterImpl::drawLayout

Call SalLayout::GetNextGlyphs with one glyph at a time while collecting
glyphs to draw, which allows us to simplify the code a bit and helps
simplify my next patch.

Change-Id: I5c9ddb7469301d8fbc6a15695c01af7b0879685a
Reviewed-on: https://gerrit.libreoffice.org/53384Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Khaled Hosny <khaledhosny@eglug.org>

vcl/source/gdi/pdfwriter_impl.hxx

@@ -810,7 +810,7 @@ i12626
     void appendLiteralStringEncrypt( OStringBuffer const & rInString, const sal_Int32 nInObjectNumber, OStringBuffer& rOutBuffer );
 
     /* creates fonts and subsets that will be emitted later */
-    void registerGlyphs(int nGlyphs, const GlyphItem** pGlyphs, sal_Int32* pGlpyhWidths, sal_Ucs* pCodeUnits, sal_Int32 const * pCodeUnitsPerGlyph, sal_uInt8* pMappedGlyphs, sal_Int32* pMappedFontObjects, const PhysicalFontFace* pFallbackFonts[]);
+    void registerGlyph(const GlyphItem* pGlyph, const PhysicalFontFace* pFont, const std::vector<sal_Ucs>& rCodeUnits, sal_uInt8& nMappedGlyph, sal_Int32& nMappedFontObject);
 
     /*  emits a text object according to the passed layout */
     /* TODO: remove rText as soon as SalLayout will change so that rText is not necessary anymore */