valgrind: update to the latest version, fix musl support

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@42978 3c298f89-4303-0410-b956-a3cf2f4a3e73
gdb: update to version 7.8, fix musl build

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@42979 3c298f89-4303-0410-b956-a3cf2f4a3e73