[support.general, depr.cpp.headers] remove index entries for now-deprecated headers and symbols, and add missing index entries for deprecated headers.

Fixes NB JP 23 (C++17 DIS)

Author: tkoeppe

source/compatibility.tex

@@ -1856,8 +1856,10 @@
 from the \Cpp standard library.
 
 \pnum
-The headers \tcode{<ciso646>}, \tcode{<cstdalign>}\iref{depr.cstdalign.syn},
-and \tcode{<cstdbool>}\iref{depr.cstdbool.syn} are meaningless in \Cpp. Use of
+The headers \tcode{<ciso646>}\indextext{\idxhdr{ciso646}},
+\tcode{<cstdalign>}\indextext{\idxhdr{cstdalign}}\iref{depr.cstdalign.syn},
+and \tcode{<cstdbool>}\indextext{\idxhdr{cstdbool}}\iref{depr.cstdbool.syn}
+are meaningless in \Cpp. Use of
 the \Cpp headers \tcode{<ccomplex>}, \tcode{<cstdalign>}, \tcode{<cstdbool>},
 and \tcode{<ctgmath>} is deprecated\iref{depr.c.headers}.
 

source/support.tex

@@ -3711,11 +3711,8 @@
 \indexlibrary{\idxhdr{csignal}}%
 \indextext{\idxhdr{cstdlib}}%
 \indexlibrary{\idxhdr{cstdlib}}%
-\indextext{\idxhdr{cstdbool}}%
-\indexlibrary{\idxhdr{cstdbool}}%
 \indexlibrary{\idxcode{getenv}}%
 \indexlibrary{\idxcode{system}}%
-\indexlibrary{\idxcode{__bool_true_false_are_defined}}%
 Headers
 \tcode{<csetjmp>} (nonlocal jumps),
 \tcode{<csignal>} (signal handling),