Fix unwanted text‑node merging on libxml2 2.12+ by manually updating doc pointers #2774

Job	Run time
Windows x64 MSVC Clang gnustep-2.2	19m 49s
Windows x64 MinGW GCC	27m 20s
Windows arm64 MSVC Clang gnustep-2.2	34m 10s
Ubuntu x64 GCC	4m 59s
Rocky Linux 8 x64 Clang gnustep-2.2	2m 15s
Rocky Linux 9 x64 Clang gnustep-2.2	5m 38s
Windows x64 MinGW Clang gnustep-2.2	25m 8s
Ubuntu x64 Clang gnustep-2.2	5m 6s
	2h 4m 25s

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