newt: Extend link tables symbols

So far for link time generated tables two symbols
were create for each table:

pkg.link_tables:
    - foo

would generate link_tables.ld.h with following content
        __foo_start__ = .;
        KEEP(*(.foo))
        KEEP(*(SORT(.foo.*)))
        __foo_end__ = .;

Now additional symbol foo will be generated it will
make it more straightforward to use link-time tables
in source code where table can be access directly
by a name specified in yml
        __foo_start__ = .;
        foo = .;
        KEEP(*(.foo))
        KEEP(*(SORT(.foo.*)))
        __foo_end__ = .;

Author: kasjer

newt/builder/extcmd.go

@@ -188,6 +188,7 @@ func getLinkTableEntry(name string) string {
 	indent := "        "
 
 	entry := indent + "__" + name + "_start__ = .;\n" +
+		indent + name + " = .;\n" +
 		indent + "KEEP(*(." + name + "))\n" +
 		indent + "KEEP(*(SORT(." + name + ".*)))\n" +
 		indent + "__" + name + "_end__ = .;\n\n"