[LyX/master] Avoid warnings with gcc 9

[Jean-Marc Lasgouttes]

commit 134f3aedaf4150367cdc2f6855d695d3791a5353
Author: Jean-Marc Lasgouttes <lasgout...@lyx.org>
Date:   Wed Jun 12 18:49:29 2019 +0200

    Avoid warnings with gcc 9
    
    The warning about unneeded std::move can be solved by conditioning on
    C++14 mode.
    
    The warnings about deprecated copy is harder, so we disable it for
    now. We will be able to fix our part, but Qt triggers it a lot too.
---
 config/lyxinclude.m4 |   11 +++++++----
 src/MetricsInfo.cpp  |    4 ++++
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/config/lyxinclude.m4 b/config/lyxinclude.m4
index a6298ac..f77e348 100644
--- a/config/lyxinclude.m4
+++ b/config/lyxinclude.m4
@@ -404,8 +404,11 @@ 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"
-  fi
+      case $gxx_version in
+         9.*) AM_CPPFLAGS="$AM_CPPFLAGS -Wall -Wextra -Wno-deprecated-copy";;
+         *) AM_CPPFLAGS="$AM_CPPFLAGS -Wall -Wextra";;
+      esac
+    fi
   case $gxx_version in
       2.*|3.*|4.@<:@0-6@:>@) AC_MSG_ERROR([gcc >= 4.7 is required]);;
   esac
@@ -874,7 +877,7 @@ AC_DEFUN([MSYS_AC_CANONICAL_PATH],
 dnl this is used by the macro blow to general a proper config.h.in entry
 m4_define([LYX_AH_CHECK_DECL],
 [AH_TEMPLATE(AS_TR_CPP(HAVE_DECL_$1),
-  [Define if you have the prototype for function `$1'])])
+  [Define if you have the prototype for function `$1'])])dnl`
 
 dnl Check things are declared in headers to avoid errors or warnings.
 dnl Called like LYX_CHECK_DECL(function, header1 header2...)
@@ -894,7 +897,7 @@ done])
 dnl this is used by the macro below to generate a proper config.h.in entry
 m4_define([LYX_AH_CHECK_DEF],
 [AH_TEMPLATE(AS_TR_CPP(HAVE_DEF_$1),
-  [Define to 1 if `$1' is defined in `$2'])])
+  [Define to 1 if `$1' is defined in `$2'])])dnl'
 
 dnl Check whether name is defined in header by using it in codesnippet.
 dnl Called like LYX_CHECK_DEF(name, header, codesnippet)
diff --git a/src/MetricsInfo.cpp b/src/MetricsInfo.cpp
index 0e90876..7eaca10 100644
--- a/src/MetricsInfo.cpp
+++ b/src/MetricsInfo.cpp
@@ -74,7 +74,11 @@ Changer MetricsBase::changeFontSet(string const & name)
            && ((isTextFont(oldname) && oldcolor != Color_foreground)
                || (isMathFont(oldname) && oldcolor != Color_math)))
                font.setColor(oldcolor);
+#if __cplusplus >= 201402L
+       return rc;
+#else
        return move(rc);
+#endif
 }