Treat static followed by extern declarations as specifying internal linkage.

See C17 section 6.2.2 p4-5.

Symbol.pas

@@ -2049,6 +2049,9 @@ if space <> fieldListSpace then begin   {are we defining a function?}
          Error(42)
       else begin
          itype := MakeCompositeType(cs^.itype, itype);
+         if class = externsy then
+            if cs^.class = staticsy then
+               class := staticsy;
          p := cs;
          needSymbol := false;
          end; {else}

cc.notes

@@ -1966,6 +1966,8 @@ int foo(int[42]);
 
 218. If a function declared within a block had the same name as a variable in an outer scope, the symbol table entry for that variable could be corrupted, leading to spurious errors or incorrect code generation. 
 
+219. If a function is first declared as "static" and then subsequently redeclared or defined as "extern" or with no storage-class specifier, it should be private to the source file, the same as if it was just declared "static".
+
 -- Bugs from C 2.1.0 that have been fixed -----------------------------------
 
 1.  In some situations, fread() reread the first 1K or so of the file.