debug messages: implement dynamic debug

Heavily inspired off linux kernel's dynamic debug:
 * add a /sys/kernel/debug/dynamic_debug/control file
 (accessible from linux side in /sys/class/mcos/mcos0/sys/kernel/debug/dynamic_debug/control)
 * read from file to list debug statements (currently limited to 4k in size)
 * write to file with '[file foo ][func bar ][line [x][-[y]]] [+-]p' to change values

Side effects:
 * reindented all linker scripts, there is a new __verbose section
 * added string function strpbrk

Change-Id: I36d7707274dcc3ecaf200075a31a2f0f76021059

arch/x86_64/elfboot/raw.lds

@@ -9,29 +9,29 @@ PHDRS
 SECTIONS
 {
 	. = SIZEOF_HEADERS;
-    . = ALIGN(4096);
+	. = ALIGN(4096);
 	.text :	{
-	      *(.text)
+		*(.text)
 	} :text
 	.data : {
-	      *(.data)
-	      *(.data.*)
+		*(.data)
+		*(.data.*)
 	} :data
 	.rodata : {
-	      *(.rodata .rodata.*)
+		*(.rodata .rodata.*)
 	} :data
 
 	. = ALIGN(8);
 	.bss : {
-	     _bss_start = .;
-	     *(.bss .bss.*)
-	     _bss_end = .;
-         . = ALIGN(4096);
-         _stack_end = .;
-    } :data
+		_bss_start = .;
+		*(.bss .bss.*)
+		_bss_end = .;
+		. = ALIGN(4096);
+		_stack_end = .;
+	} :data
 
 	/DISCARD/ : {
-	     *(.eh_frame)
-         *(.note.gnu.build-id)
+		*(.eh_frame)
+		*(.note.gnu.build-id)
 	}
-}
+}