Character and word spacing (Tc and Tw parameters) should also apply at end of strings

[dhdaines]

The way character spacing (PDF 2.0 section 9.3.2) is applied is needlessly complex and also incorrect in pdfminer.six. Instead of applying spacing between the glyphs in a single text-showing operator, it should simply apply it to the glyph displacement, such that it "carries over" to the next text-showing operator.

For this PDF: character_spacing.pdf

pdfminer.six (in PDFTextDevice.render_string_horizontal) will currently do something like this:

when it should do this:

[dhdaines]

(this is also true for word spacing but it appears that pdfminer.six does that correctly)