updfparser: unstable 2023-01-23 -> 2023-08-08

Without the change build fails against gcc-13 as:

    $ nix build --impure --expr 'with import ./. {}; updfparser.override { stdenv = gcc13Stdenv; }'
    error: builder for '/nix/store/8p5hwa50rild5yaijxg9iavr3lyvi3w2-updfparser.drv' failed with exit code 2;
       last 10 log lines:
       > building
       > build flags: SHELL=/nix/store/xdqlrixlspkks50m9b0mpvag65m3pf2w-bash-5.2-p15/bin/bash BUILD_STATIC=1 BUILD_SHARED=1
       > mkdir obj
       > g++ -Wall -fPIC -I./include -O2 -c src/uPDFParser.cpp -o obj/uPDFParser.o
       > In file included from ./include/uPDFParser.h:34,
       >                  from src/uPDFParser.cpp:26:
       > ./include/uPDFObject.h:49:52: error: 'uint64_t' has not been declared
       >    49 |         Object(int objectId, int generationNumber, uint64_t offset, bool isNew=false,
       >       |                                                    ^~~~~~~~