[tables] Redefine methods for accessing linker tables

Intel's C compiler (icc) chokes on the zero-length arrays that we
currently use as part of the mechanism for accessing linker table
entries.  Abstract away the zero-length arrays, to make a port to icc
easier.

Introduce macros such as for_each_table_entry() to simplify the common
case of iterating over all entries in a linker table.

Represent table names as #defined string constants rather than
unquoted literals; this avoids visual confusion between table names
and C variable or type names, and also allows us to force a
compilation error in the event of incorrect table names.

src/core/process.c

@@ -31,12 +31,6 @@
 /** Process run queue */
 static LIST_HEAD ( run_queue );
 
-/** Registered permanent processes */
-static struct process processes[0]
-	__table_start ( struct process, processes );
-static struct process processes_end[0]
-	__table_end ( struct process, processes );
-
 /**
  * Add process to process list
  *
@@ -93,9 +87,8 @@ void step ( void ) {
 static void init_processes ( void ) {
 	struct process *process;
 
-	for ( process = processes ; process < processes_end ; process++ ) {
+	for_each_table_entry ( process, PERMANENT_PROCESSES )
 		process_add ( process );
-	}
 }
 
 /** Process initialiser */