Update package to latest stable version (1.7.3)

Signed-off-by: Jean-Michel Julien <jean-michel.julien@trilliantinc.com>

$(CP) was defined as `cp -fpR' since the very begining of OpenWrt build
system (2006-06-22).  The -R option should be enough and base packages
use only $(CP) for the same purposes just fine and BSD manual of cp also
discourages the use of `-r' option.  So let's just tidy up the usage now.

Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>

POrtable COmponents is a Modern, powerful open source C++ class libraries
for building network- and internet-based applications that run on desktop,
 server, mobile and embedded systems.

Original Makefile -->
https://dev.openwrt.org/browser/packages/libs/poco/Makefile

add license
add maintainer
update URL to latest github stable version (1.7.0)
change patch to the configure file
add a patch to build with musl-libc

Signed-off-by: Jean-Michel Julien <jean-michel.julien@trilliantinc.com>