LibPDF: Implement most of the spec algorithm for picking TrueType glyphs

Non-CID-keyed fonts in PDFs have 8-bit codepoints which are mapped from
bytes to character names via encoding.

TrueType fonts don't index glyphs by name (Type1 fonts do), so the fix
(codified in the spec) was to make a list of all possible glyph names
and map those to (16-bit) unicode values, and then pass those into the
truetype cmap.

(As a fallback, we're supposed to look at the optional names in the
font's "post" table. That part isn't implemented here yet.)

Userland/Libraries/LibPDF/CMakeLists.txt

@@ -6,6 +6,7 @@ set(SOURCES
     Encoding.cpp
     Encryption.cpp
     Filter.cpp
+    Fonts/AdobeGlyphList.cpp
     Fonts/CFF.cpp
     Fonts/PDFFont.cpp
     Fonts/PS1FontProgram.cpp