package/upmpdcli: add patch to fix error not detecting jsoncpp

package/upmpdcli: add patch to fix error not detecting jsoncpp

Fixes:
http://autobuild.buildroot.net/results/205463c9ea8651911972c2835e28ded1912c811a
http://autobuild.buildroot.net/results/5e9279ee60c11a3dacacf6d78f87f8d1b92968f5
http://autobuild.buildroot.net/results/97043f8defd5a59ae39b4c7f095a10d15c7fe632
http://autobuild.buildroot.net/results/e775126d5939093289b1a833dd6323ac293322ed
.. and many more.

libmpdclient, libmicrohttpd and jsoncpp provide a .pc file. Use
pkg-config for detecting the libraries and for providing the necessary
details for compiling and linking.

The current build system of upmpdcli does not use PKG_CHECK_MODULES, but
AC_LINK_IFELSE to detect jsoncpp. After bumping jsoncpp version from
1.7.2 to 1.7.5 the detection fails, because the test program does not
compile anymore:

"""
In file included from
/usr/arm-buildroot-linux-gnueabi/sysroot/usr/include/json/autolink.h:9:0,
                 from
/usr/arm-buildroot-linux-gnueabi/sysroot/usr/include/json/json.h:9,
                 from test.c:1:
/usr/arm-buildroot-linux-gnueabi/sysroot/usr/include/json/config.h:155:9:
error: 'int64_t' does not name a type
 typedef int64_t Int64;
         ^
/usr/arm-buildroot-linux-gnueabi/sysroot/usr/include/json/config.h:156:9:
error: 'uint64_t' does not name a type
 typedef uint64_t UInt64;
         ^
/usr/arm-buildroot-linux-gnueabi/sysroot/usr/include/json/config.h:158:9:
error: 'Int64' does not name a type
 typedef Int64 LargestInt;
         ^
/usr/arm-buildroot-linux-gnueabi/sysroot/usr/include/json/config.h:159:9:
error: 'UInt64' does not name a type
 typedef UInt64 LargestUInt;
         ^
In file included from
/usr/arm-buildroot-linux-gnueabi/sysroot/usr/include/json/json.h:10:0,
                 from test.c:1:
/usr/arm-buildroot-linux-gnueabi/sysroot/usr/include/json/value.h:184:11:
error: 'UInt64' in namespace 'Json' does not name a type
   typedef Json::UInt64 UInt64;

[..]
"""

Instead of fixing the test program use PKG_CHECK_MODULES to check for
jsoncpp. While we're on it, add it for libmpdclient and libmicrohttpd,
too.

Upstream-status: https://github.com/medoc92/upmpdcli/pull/52

Signed-off-by: Jörg Krause <joerg.krause@embedded.rocks>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>