Add missing pkg-config defns where required

configure.ac

@@ -37,6 +37,28 @@ AC_PROG_INSTALL
 AC_PROG_MAKE_SET
 
 PKG_PROG_PKG_CONFIG
+
+m4_ifndef([PKG_INSTALLDIR],[
+# PKG_INSTALLDIR(DIRECTORY)
+# -------------------------
+# Substitutes the variable pkgconfigdir as the location where a module
+# should install pkg-config .pc files. By default the directory is
+# $libdir/pkgconfig, but the default can be changed by passing
+# DIRECTORY. The user can override through the --with-pkgconfigdir
+# parameter.
+AC_DEFUN([PKG_INSTALLDIR],
+[m4_pushdef([pkg_default], [m4_default([$1], ['${libdir}/pkgconfig'])])
+m4_pushdef([pkg_description],
+    [pkg-config installation directory @<:@]pkg_default[@:>@])
+AC_ARG_WITH([pkgconfigdir],
+    [AS_HELP_STRING([--with-pkgconfigdir], pkg_description)],,
+    [with_pkgconfigdir=]pkg_default)
+AC_SUBST([pkgconfigdir], [$with_pkgconfigdir])
+m4_popdef([pkg_default])
+m4_popdef([pkg_description])
+]) dnl PKG_INSTALLDIR
+])
+
 PKG_INSTALLDIR
 
 AC_SUBST([PACKAGE_VERSION_MAJOR],package_version_major)
@@ -221,6 +243,7 @@ AC_CONFIG_FILES([\
     test/Makefile \
     doc/Makefile \
     Makefile \
+    erasurecode.pc \
     Xorcode.pc
 ])