Use pkg-config instead of ${PYTHON}-config to find python

diff -uNr pidgin-2.10.12.orig/configure.ac pidgin-2.10.12/configure.ac
--- pidgin-2.10.12.orig/configure.ac	2016-01-01 00:19:40.000000000 +0100
+++ pidgin-2.10.12/configure.ac	2016-05-05 16:55:13.258945925 +0200
@@ -1585,20 +1585,15 @@
 dnl Check for Python headers (currently useful only for libgnt)
 dnl (Thanks to XChat)
 if test "x$enable_consoleui" = "xyes" -a ! -z "$PYTHON" -a x"$PYTHON" != x"no" ; then
-	AC_MSG_CHECKING(for Python compile flags)
-	if test -f ${PYTHON}-config; then
-		PY_CFLAGS=`${PYTHON}-config --includes`
-		PY_LIBS=`${PYTHON}-config --libs`
-		AC_DEFINE(USE_PYTHON, [1], [Define if python headers are available.])
-		AC_MSG_RESULT(ok)
-	else
-		AC_MSG_RESULT([Cannot find ${PYTHON}-config])
-		PY_CFLAGS=""
-		PY_LIBS=""
-	fi
+        AC_MSG_CHECKING(for Python compile flags)
+        PKG_CHECK_MODULES(PY, python, [
+                AC_SUBST(PY_CFLAGS)
+                AC_SUBST(PY_LIBS)
+        ], [
+                AC_MSG_RESULT(no)
+                AC_MSG_ERROR([Can't find python])
+        ])
 fi
-AC_SUBST(PY_CFLAGS)
-AC_SUBST(PY_LIBS)
 
 dnl #######################################################################
 dnl # Check for Mono support