[libc-commits] [libc] [libc][docs] Generate docs for signal.h & optimized is_implemented func (PR #88028)

[Nick Desaulniers via libc-commits]

================
@@ -0,0 +1,21 @@
+{
+  "macros": [
+    "__STDC_VERSION_FENV_H__"
----------------
nickdesaulniers wrote:

7.14 also mentions a few addition macros:
- `SIG_DFL`
- `SIG_ERR`
- `SIG_IGN`

and a few more.  I actually find section `B.13 Signal handling <signal.h>` easier to view a concise summary of what's expected to be found where (though in n3096 it lacks a mention of `__STDC_VERSION_FENV_H__` which seems like a minor mistake in the spec).

Please add those, too, even if we aren't generating documentation for them yet today.

https://github.com/llvm/llvm-project/pull/88028