A few updates to the pdf device

Ensure that only base14 fonts are used
Set BaseFont using the name from the font
Use WinAnsiEncoding
Derive the font size from the trm matrix
Add support for freetext annotations

This initial commit doesn't entirely complete the task:
1) There are a couple of ucs<->winansi conversions left out,
2) The text displayed by the appearance string can slightly
overflow the annotation rectangle.
Change pdf_measure_text to account for the borders around characters

Prevously the true bounds of the glyph were used which didn't account
for the total area blocked out by a character
For freetext annotations, distinguish device and page space correctly.
Fix signature-support build
Improve naming consistency
Handle more color cases in DA handling
Correctly account for alterations to xobject matrix and bbox
Use ascender and descender to determine line skip

We should use the leading, if present, and if not present we should
probably use a value a little greater than the sum of the ascender
and descender, but this is definitely a step in the right direction
and improves the look of filled-in forms.
Add support for creating signature-field appearance streams
Insert the extra layers required for a signature-appearance stream
Remove unnecessary parameter
Signature creation
Merge branch 'release' into 'master'.
Use unscaled metrics in xps_measure_font_glyph.
Include platform source files in "make tags".
Update source code browser html generation scripts for new layout.
Enable horizontal mouse scrolling in X11.

Based on a patch from Sebastian Neuser - many thanks.

Use mouse buttons 6 and 7 to do the same as 4 and 5, but with Y
rather than X being the default.
Bug 694522: Cope with selection of text on a JPEG image.

If there is no text to select we return an array with a NULL in it
and this causes the code to crash. Simple workaround.
Add -F flag to mudraw to allow format selection.

This allows us to "mudraw -F ppm -o /dev/null" etc.