#12 use @libdir@ in quickfix.pc.in

[echion]

This patch has been in Fedora's quickfix RPM build since (at least)
2008-11-07 [1] and appears to have been written by Hayden
James[1].

1. https://koji.fedoraproject.org/koji/buildinfo?buildID=70180

$ svn diff
Index: quickfix.pc.in
===================================================================
--- quickfix.pc.in (revision 2235)
+++ quickfix.pc.in (working copy)
@@ -1,6 +1,6 @@
prefix=@prefix@
exec_prefix=@prefix@
-libdir=@prefix@/lib
+libdir=@libdir@
includedir=@prefix@/include

Name: QuickFIX

[echion]

Thanks!