libc: document posix_spawnattr_{get,set}procdescp_np(3)

[kib]

Reword the unclear and long sentence.

[asomers]

I suggest a few wording changes. Also, fork->vfork, pdfork->pdrfork, and execfd->procdescp.

lib/libc/gen/posix_spawnattr_getprocdescp_np.3

42

46–47

48–49

50–57

59–63

67

68

71

76

[kib]

lib/libc/gen/posix_spawnattr_getprocdescp_np.3

50–57

vfork is an implementation detail, that can change and that not relevant to the reader.
I listed all of them in one xref to make it not a point.

67

Well, it is pdfork(2) part of the procdesc man page that describes flags, and both pdrfork and this place reference it.
So I think it is more correct, and more future-proof if the pdrfork is moved into a separate man page.

This is my opinion, if you insist, I will change this.

[kib]

Alan' editing.