Buildsystem fixes for proper respecting multilib-aware systems

Gentoo bugreport: https://bugs.gentoo.org/show_bug.cgi?id=496430

--- Makefile.orig	2012-03-22 15:15:59.000000000 +0400
+++ Makefile	2013-12-31 13:50:16.434307159 +0400
@@ -108,14 +108,15 @@
 prefix = $(ac_prefix)
 
 install:
-	mkdir -p $(DESTDIR)$(prefix)/lib
-	cp -f $(APP_LIB_FILES) $(DESTDIR)$(prefix)/lib/
+	mkdir -p $(DESTDIR)$(PJ_INSTALL_LIB_DIR)
+	cp -f $(APP_LIB_FILES) $(DESTDIR)$(PJ_INSTALL_LIB_DIR)/
 	mkdir -p $(DESTDIR)$(prefix)/include
 	for d in pjlib pjlib-util pjnath pjmedia pjsip; do \
 		cp -RLf $$d/include/* $(DESTDIR)$(prefix)/include/; \
 	done
-	mkdir -p $(DESTDIR)$(prefix)/lib/pkgconfig
-	sed -e "s!@PREFIX@!$(DESTDIR)$(prefix)!" libpjproject.pc.in | \
+	mkdir -p $(DESTDIR)$(PJ_INSTALL_LIB_DIR)/pkgconfig
+	sed -e "s!@PREFIX@!$(prefix)!" libpjproject.pc.in | \
+		sed -e "s!@LIBDIR@!$(PJ_INSTALL_LIB_DIR)!" | \
 		sed -e "s/@PJ_VERSION@/$(PJ_VERSION)/" | \
 		sed -e "s!@PJ_LDLIBS@!$(PJ_LDLIBS)!" | \
-		sed -e "s!@PJ_INSTALL_CFLAGS@!$(PJ_INSTALL_CFLAGS)!" > $(DESTDIR)/$(prefix)/lib/pkgconfig/libpjproject.pc
+		sed -e "s!@PJ_INSTALL_CFLAGS@!$(PJ_INSTALL_CFLAGS)!" > $(DESTDIR)/$(PJ_INSTALL_LIB_DIR)/pkgconfig/libpjproject.pc
--- libpjproject.pc.in.orig	2013-12-31 13:51:08.459302831 +0400
+++ libpjproject.pc.in	2013-12-31 13:51:16.857302132 +0400
@@ -2,7 +2,7 @@
 
 prefix=@PREFIX@
 exec_prefix=${prefix}
-libdir=${exec_prefix}/lib
+libdir=@LIBDIR@
 includedir=${prefix}/include
 
 Name: libpjproject
--- build.mak.in.orig	2013-12-31 13:52:22.492296672 +0400
+++ build.mak.in	2013-12-31 13:52:06.722297984 +0400
@@ -163,7 +163,7 @@
 # library from the install location (i.e. --prefix)
 export PJ_INSTALL_DIR := @prefix@
 export PJ_INSTALL_INC_DIR := $(PJ_INSTALL_DIR)/include
-export PJ_INSTALL_LIB_DIR := $(PJ_INSTALL_DIR)/lib
+export PJ_INSTALL_LIB_DIR := @libdir@
 export PJ_INSTALL_CFLAGS := -I$(PJ_INSTALL_INC_DIR) -DPJ_AUTOCONF=1	@CFLAGS@
 export PJ_INSTALL_CXXFLAGS := $(PJ_INSTALL_CFLAGS)
 export PJ_INSTALL_LDFLAGS := -L$(PJ_INSTALL_LIB_DIR) $(APP_LDLIBS)