Stop redefining libdir, use moduledir for ${libdir}/xrdp

libdir is for shared and static libraries. Some xrdp libraries are loaded
dynamically from a non-standard directory, so they are used like modules.

Having separate libdir and moduledir would eventually allow to separate
dynamically loaded modules from shared libraries.

mc/Makefile.am

@@ -7,7 +7,7 @@ AM_CPPFLAGS = \
   -DXRDP_PID_PATH=\"${localstatedir}/run\" \
   -I$(top_srcdir)/common
 
-lib_LTLIBRARIES = \
+module_LTLIBRARIES = \
   libmc.la
 
 libmc_la_SOURCES = mc.c