package/spice: needs C++

spice needs C++ since bump to version 0.15.0 in commit
b784f1bc0fc3ac33a20549069a81ff98260b58e9 and
https://github.com/freedesktop/spice/commit/e6e6ded681ff154f236f260f071389c4c8c0d944:

configure: error: *** A compiler with support for C++11 language features is required.

Fixes:
 - http://autobuild.buildroot.org/results/4e0dc43c28d45176cccf573fb56ea9690192f754

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/spice/Config.in

@@ -1,12 +1,14 @@
-comment "spice server needs a toolchain w/ wchar, threads"
+comment "spice server needs a toolchain w/ wchar, threads, C++"
 	depends on BR2_i386 || BR2_x86_64
-	depends on !BR2_USE_WCHAR || !BR2_TOOLCHAIN_HAS_THREADS
+	depends on !BR2_USE_WCHAR || !BR2_TOOLCHAIN_HAS_THREADS || \
+		!BR2_INSTALL_LIBSTDCPP
 
 config BR2_PACKAGE_SPICE
 	bool "spice server"
 	depends on BR2_i386 || BR2_x86_64
 	depends on BR2_USE_WCHAR # libglib2
 	depends on BR2_TOOLCHAIN_HAS_THREADS # libglib2
+	depends on BR2_INSTALL_LIBSTDCPP
 	select BR2_PACKAGE_JPEG
 	select BR2_PACKAGE_LIBGLIB2
 	select BR2_PACKAGE_OPENSSL