sstp-client: new appication has been ported in packages feeds under net/sstp-client (version 1.0.9)

From: Federico Di Marco fededim@gmail.com

Body of explanation:
A new package has been added in packages feed under net/sstp-client directory, porting a simple SSTP client for Linux (please see http://sstp-client.sourceforge.net) to OpenWRT. There was also an old ticket requesting the porting of this tool (https://dev.openwrt.org/ticket/10411). The libevent library used by this tool has been updated as well (it was necessary).

Signed-off-by: Federico Di Marco fededim@gmail.com
You don't need this line, $(INSTALL_DIR) works like mkdir -p  (Same for /usr above)