Fix pthread_t initialization issues in testThreads.c and libxml2

[SoftwareRat]

This pull request addresses a compatibility issue with pthread_t initialization in libxml2 for modern toolchains. The main change ensures that thread IDs are properly zero-initialized, and the patch is now applied during the build process.

Thread initialization fix

• Updated patches/libxml2-2.7.8-pthread.patch to replace the assignment of (pthread_t) -1 with memset to zero-initialize pthread_t variables, improving compatibility with modern compilers.

Build script update

• Modified scripts/012-libxml2-2.7.8.sh to apply the pthread patch automatically during the build, ensuring the fix is consistently used.

[zeldin]

Huh. The patch is applied with -p1, and yet there is no filename given in the patch file. How is that supposed to work?

Also, I can't find any file in libxml2-2.7.8.tar.gz that contains this exact code. There is similar code in testThreads.c, but it is lacking the #if present in this patch...

If if acually is testThreads you are trying to alter, then

1. tid[i] will be overwritten by pthread_create immediately afterwards, so there is no need to initialize any part of it. The assignment can just be removed.
2. That is a testcase, do we even run them?