New pdfioFileCreateFontObjFromSystem API

[michaelrsweet]

New API for creating font objects from system fonts:

extern pdfio_obj_t *pdfioFileCreateFontObjFromSystem(pdfio_file_t *pdf, const char *family, pdfio_style_t style, pdfio_weight_t weight, pdfio_stretch_t stretch, bool unicode);