[LyX/2.3.x] Disable deprecated-copy warning with clang10 and gcc10

[Jean-Marc Lasgouttes]

commit 7898e0741260ad0454d81d3c1bedffe46dde4526
Author: Jean-Marc Lasgouttes <lasgouttes at lyx.org>
Date:   Tue Apr 28 13:16:45 2020 +0200

    Disable deprecated-copy warning with clang10 and gcc10
    
    This was already done for gcc9 and saves tons of warnings.
    
    Note that the warning in Qt are gone with Qt5.13, so eventually we
    will have to get rid of our own copy issues.
    
    (cherry picked from commit e9e8069b170ef3128402bc6e6f657339da1760a2)
    (cherry picked from commit db5021c42eb5828c3fa0fd786b14eafcf9fed52f)
---
 config/lyxinclude.m4 |    6 ++++--
 status.23x           |    1 +
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/config/lyxinclude.m4 b/config/lyxinclude.m4
index 164b2f7..59421ae 100644
--- a/config/lyxinclude.m4
+++ b/config/lyxinclude.m4
@@ -410,9 +410,11 @@ if test x$GXX = xyes; then
   fi
   dnl Warnings are for preprocessor too
   if test x$enable_warnings = xyes ; then
+      AM_CPPFLAGS="$AM_CPPFLAGS -Wall -Wextra"
       case $gxx_version in
-	  9.*) AM_CPPFLAGS="$AM_CPPFLAGS -Wall -Wextra -Wno-deprecated-copy";;
-	  *) AM_CPPFLAGS="$AM_CPPFLAGS -Wall -Wextra";;
+	  9.*|10.*|clang-10*)
+	      AM_CXXFLAGS="$AM_CXXFLAGS -Wno-deprecated-copy";;
+	  *);;
       esac
     fi
   case $gxx_version in
diff --git a/status.23x b/status.23x
index 098a400..2f045e8 100644
--- a/status.23x
+++ b/status.23x
@@ -144,3 +144,4 @@ What's new
 
 - Download dictionary and thesaurus files, on Windows, from our SVN repo (bug 11192).
 
+- Avoid many warnings with g++ 10 and clang++ 10.