libev: bump to version 4.15

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/libev/libev.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-LIBEV_VERSION = 4.11
+LIBEV_VERSION = 4.15
 LIBEV_SITE = http://dist.schmorp.de/libev/
 LIBEV_INSTALL_STAGING = YES
 LIBEV_LICENSE = BSD-2c or GPLv2+