libmad pkg-config patch, adapted from Arch Linux package. Needs to run autoreconf.

libmad-pkg-config.diff

diff -Naur libmad-0.15.1b.orig/configure.ac libmad-0.15.1b/configure.ac
--- libmad-0.15.1b.orig/configure.ac	2004-01-23 10:41:32.000000000 +0100
+++ libmad-0.15.1b/configure.ac	2015-10-12 05:51:12.514078692 +0200
@@ -26,7 +26,7 @@
 
 AC_CONFIG_SRCDIR([decoder.h])
 
-AM_INIT_AUTOMAKE
+AM_INIT_AUTOMAKE([foreign])
 
 AM_CONFIG_HEADER([config.h])
 
@@ -429,5 +429,5 @@
 dnl AC_SUBST(LTLIBOBJS)
 
 AC_CONFIG_FILES([Makefile msvc++/Makefile  \
-	libmad.list])
+	libmad.list mad.pc])
 AC_OUTPUT
diff -Naur libmad-0.15.1b.orig/mad.pc.in libmad-0.15.1b/mad.pc.in
--- libmad-0.15.1b.orig/mad.pc.in	1970-01-01 01:00:00.000000000 +0100
+++ libmad-0.15.1b/mad.pc.in	2015-10-12 05:31:43.851805494 +0200
@@ -0,0 +1,10 @@
+prefix=@prefix@
+exec_prefix=@exec_prefix@
+libdir=@libdir@
+includedir=@includedir@
+
+Name: MAD
+Description: libmad - MPEG audio decoder library
+Version: @VERSION@
+Libs: -L${libdir} -lmad
+Cflags:
diff -Naur libmad-0.15.1b.orig/Makefile.am libmad-0.15.1b/Makefile.am
--- libmad-0.15.1b.orig/Makefile.am	2004-02-17 03:02:03.000000000 +0100
+++ libmad-0.15.1b/Makefile.am	2015-10-12 05:31:43.831805227 +0200
@@ -33,9 +33,12 @@
 minimad_INCLUDES =	
 minimad_LDADD =		libmad.la
 
-EXTRA_DIST =		mad.h.sed  \
+EXTRA_DIST =		mad.h.sed mad.pc.in \
 			CHANGES COPYRIGHT CREDITS README TODO VERSION
 
+pkgconfigdir = $(libdir)/pkgconfig
+pkgconfig_DATA= mad.pc
+
 exported_headers =	version.h fixed.h bit.h timer.h stream.h frame.h  \
 			synth.h decoder.h