plugin: add core code

Signed-off-by: Emilio G. Cota <cota@braap.org>
[AJB: moved directory and merged various fixes]
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
diff --git a/configure b/configure
index 145fcab..d6fbcf4 100755
--- a/configure
+++ b/configure
@@ -3616,6 +3616,9 @@
 if test "$modules" = yes; then
     glib_modules="$glib_modules gmodule-export-2.0"
 fi
+if test "$plugins" = yes; then
+    glib_modules="$glib_modules gmodule-2.0"
+fi
 
 # This workaround is required due to a bug in pkg-config file for glib as it
 # doesn't define GLIB_STATIC_COMPILATION for pkg-config --static