libsupc++: add <compare> to precompiled header

Also process it with Doxygen.

	* doc/doxygen/user.cfg.in (INPUT): Add <compare> header.
	* include/precompiled/stdc++.h: Include <compare> header.

From-SVN: r277944

libstdc++-v3/ChangeLog

 2019-11-07  Jonathan Wakely  <jwakely@redhat.com>
 
+	* doc/doxygen/user.cfg.in (INPUT): Add <compare> header.
+	* include/precompiled/stdc++.h: Include <compare> header.
+
 	* libsupc++/compare (common_comparison_category)
 	(common_comparison_category_t): Define for C++20.
 	* testsuite/18_support/comparisons/common/1.cc: New test.

libstdc++-v3/doc/doxygen/user.cfg.in

@@ -787,6 +787,7 @@ WARN_LOGFILE           =
 # Note: If this tag is empty the current directory is searched.
 
 INPUT                  = @srcdir@/doc/doxygen/doxygroups.cc \
+                         @srcdir@/libsupc++/compare \
                          @srcdir@/libsupc++/cxxabi.h \
                          @srcdir@/libsupc++/exception \
                          @srcdir@/libsupc++/initializer_list \

libstdc++-v3/include/precompiled/stdc++.h

@@ -135,7 +135,7 @@
 
 #if __cplusplus > 201703L
 #include <bit>
-// #include <compare>
+#include <compare>
 #include <concepts>
 #include <numbers>
 #include <ranges>