_nc_env_access also denies non-root users from reading env vars

[Arnavion]

Hello,

I noticed that programs using ncurses 6.2 were not taking
the TERMINFO and TERMINFO_DIRS env vars into account,
and tracked it down to the 20210626 patch.

The debugger shows me that _nc_env_access always returns FALSE,
which means use_terminfo_vars evaluates to FALSE,
which means _nc_first_db ignores the env vars. My distro package
was configured with `--disable-root-environ` but I experienced this
even when not running the programs as root.

That patch restructured _nc_env_access along these lines:

-    if (getuid() != geteuid()
-       || getgid() != getegid())
-       return FALSE;
-    /* ...finally, disallow root */
-    return (getuid() != ROOT_UID) && (geteuid() != ROOT_UID);

+    int result = TRUE;
+
+    if (is_elevated()) {
+       result = FALSE;
+    } else if ((getuid() != ROOT_UID) && (geteuid() != ROOT_UID)) {
+       result = FALSE;
+    }
+    return result;

>From my understanding of what `--disable-root-environ` is meant for
and what the code is doing in response to it, I believe the test for
getuid() / geteuid() != ROOT_UID ought to have been reversed
as part of this change? That is, it should've been:

+    } else if ((getuid() == ROOT_UID) || (geteuid() == ROOT_UID)) {
+       result = FALSE;
+    }

Is my understanding correct?

Thanks,
Arnav Singh