Added code that allows any external PROCs not beginning with B or C to be handled as normal

This shows that my current scheme is a bit of a hack; if an occam programmer starts a normal PROC with B or C, it will be treated funny during separate compilation.  In future I probably need some new form of #PRAGMA to support separate compilation, different from that used to interface with C.

backends/GenerateC.hs

@@ -2015,7 +2015,7 @@ cgenProcCall n as
             (A.Recursive, _) ->
               let m = A.nameMeta n
               in call genPar A.PlainPar $ A.Only m $ A.ProcCall m n as
-            (_, Just _) ->
+            (_, Just _) | head (A.nameName n) `elem` ['B', 'C'] ->
                  do let (c:cs) = A.nameName n
                     tell ["{int ext_args[] = {"]
                     -- We don't use the formals in csExternals because they won't