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

kernel/pager.c

@@ -21,6 +21,7 @@
 #include <kmalloc.h>
 #include <process.h>
 #include <swapfmt.h>
+#include <debug.h>
 
 #define O_RDONLY	00000000
 #define O_WRONLY	00000001
@@ -44,11 +45,8 @@
 //#define DEBUG_PRINT_PROCESS
 
 #ifdef DEBUG_PRINT_PROCESS
-#define dkprintf(...) kprintf(__VA_ARGS__)
-#define ekprintf(...) kprintf(__VA_ARGS__)
-#else
-#define dkprintf(...) do { if (0) kprintf(__VA_ARGS__); } while (0)
-#define ekprintf(...) kprintf(__VA_ARGS__)
+#undef DDEBUG_DEFAULT
+#define DDEBUG_DEFAULT DDEBUG_PRINT
 #endif
 
 /*