Compile on Slackware64 14.2 (libevent)
On `Slackware x64 14.2`, latest version of `libevent` is `2.0.22-stable`  

**build commands**
```
export MONERO_ROOT=/home/crypto/local/build/build-monero/monero-src-v0.14.0.2
export MONERO_BUILD_ROOT=$MONERO_ROOT/../build-monero-v0.14.0.2

make

Requested 'libevent >= 2.1' but version of libevent is 2.0.22-stable
```
Changing Makefile line 65 and 77  
from `"libevent >= 2.1" \`  
to `"libevent >= 2.0" \`
fixes that.

Does this break anything?
