Added library reference em_libref to EMD interface.

Occasionally dynamically drivers suffer from not being to refer to
content in the C library. Therefore I added a mechanism to allow
a C library for a certian target to define a symbol that will be
handed over to dynamic drivers for that target. Then the drivers
can use their refernce to that symbol to access content in the C
library.

libsrc/c16/emd/c16-ram.s

@@ -24,16 +24,20 @@
         .byte   $65, $6d, $64           ; "emd"
         .byte   EMD_API_VERSION         ; EM API version number
 
-; Jump table.
+; Library reference
 
-        .word   INSTALL
-        .word   UNINSTALL
-        .word   PAGECOUNT
-        .word   MAP
-        .word   USE
-        .word   COMMIT
-        .word   COPYFROM
-        .word   COPYTO
+        .addr   $0000
+
+; Jump table
+
+        .addr   INSTALL
+        .addr   UNINSTALL
+        .addr   PAGECOUNT
+        .addr   MAP
+        .addr   USE
+        .addr   COMMIT
+        .addr   COPYFROM
+        .addr   COPYTO
 
 ; ------------------------------------------------------------------------
 ; Constants

libsrc/c16/libref.s

@@ -0,0 +1,8 @@
+;
+; Oliver Schmidt, 2013-05-31
+;
+
+        .export         em_libref
+        .import         _exit
+
+em_libref       := _exit