[LIBS] netstack: Replace string.h with libs/stringlib.h in lwIP source

Signed-off-by: Anup Patel <anup@brainfault.org>
[LIBS] netstack: suppress warnings for using char as array subscripts in lwIP

Signed-off-by: Anup Patel <anup@brainfault.org>
Merge remote-tracking branch 'upstream/master' into dev_exynos4
[CORE] Increase default values of MAX_VCPU_COUNT and MAX_GUEST_COUNT

The MAX_VCPU_COUNT and MAX_GUEST_COUNT were too low. We have doubled both the limits.

If required we will increase this values even further but gradually.

Signed-off-by: Anup Patel <anup@brainfault.org>
Merge remote-tracking branch 'upstream/master' into dev_exynos4