add support for CIDToGIDMap in PDF fonts

[paulswartz]

The font spec:

{
    'CIDToGIDMap': <PDFStream(281): raw=130, {'Filter': /FlateDecode, 'Length': 128}>,
    'W': [3, 3, 250, 10, 10, 180, 13, 13, 500, 15, [250, 333, 250, 278, 500, 500, 500, 500], 29, 30, 278, 34, 34, 444, 36, [722, 667, 667], 40, [611, 556, 722, 722, 333, 389], 47, [611, 889, 722, 722], 54, [556, 611], 58, 58, 944, 68, [444, 500, 444, 500, 444, 333, 500, 500, 278, 278, 500, 278, 778, 500, 500, 500, 500, 333, 389, 278, 500, 500, 722, 500, 500, 444], 179, 180, 444, 182, 182, 333], 
    'Encoding': /Identity-H, 
    'BaseFont': /AAAMDB+font0000000016932ad6, 
    'CIDSystemInfo': {'Ordering': 'Identity', 'Supplement': 0, 'Registry': 'Adobe'}, 
    'Subtype': /CIDFontType2, 
    'FontDescriptor': {
        'FontFile2': <PDFStream(282): raw=30418, {'Filter': /FlateDecode, 'Length': 30416, 'Length1': 41480}>, 
        'FontName': /AAAMDB+font0000000016932ad6, 
        'Descent': -216, 
        'FontBBox': [-568, -307, 2000, 1006], 
        'CapHeight': 792, 
        'Type': /FontDescriptor, 
        'MaxWidth': 2000, 
        'StemV': 0, 
        'Flags': 32, 
        'XHeight': 594, 
        'Leading': 42, 
        'ItalicAngle': 0, 
        'Ascent': 891}, 
    'DW': 1000, 
    'Type': /Font}