Kernel: Rewrite ProcFS.

Now the filesystem is generated on-the-fly instead of manually adding and
removing inodes as processes spawn and die.

The code is convoluted and bloated as I wrote it while sleepless. However,
it's still vastly better than the old ProcFS, so I'm committing it.

I also added /proc/PID/fd/N symlinks for each of a process's open fd's.

Kernel/StdLib.cpp

@@ -92,10 +92,10 @@ int strcmp(const char *s1, const char *s2)
 
 char* strdup(const char *str)
 {
-    dword len = strlen(str);
-    char *s = (char*)kmalloc(len);
-    memcpy(s, str, len);
-    return s;
+    size_t len = strlen(str);
+    char* new_str = (char*)kmalloc(len + 1);
+    strcpy(new_str, str);
+    return new_str;
 }
 
 int memcmp(const void* v1, const void* v2, size_t n)