This implements a pre-decoded wchan in /proc using kallsyms.  I.e.:

        [21:23:17]rml@phantasy:~$ cat /proc/1228/wchan
        wait4

Which, aside from being cool, means procps will not have to parse
Sysyem.map for each process.  In fact, procps will no longer require
System.map.

If CONFIG_KALLSYMS is not enabled, /proc/#/wchan does not exist to
conserve memory.  Regardless of CONFIG_KALLSYMS's value, the old wchan
field in /proc/#/stat still exists.

I have a procps patch I will merge once this is in your tree.