package/libevent: bump to version 2.1.10

package/libevent: bump to version 2.1.10

See: https://github.com/libevent/libevent/releases/tag/release-2.1.10-stable

Also fix check-package warning.

Fixes:

$. ./utils/check-package package/libevent/* -v
package/libevent/0001-Disable-building-test-programs.patch:4: generate your patches with 'git format-patch -N'
Subject: [PATCH 1/2] Disable building test programs
76 lines processed
1 warnings generated

Signed-off-by: Pierre-Jean Texier <pjtexier@koncepto.io>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>