upcoming elfdump refactoring

[Luigi Rizzo]

I need to extract value and size of some symbols from an ELF file,
and make them available to a C program, something like
 
    nm -S /boot/kernel/kernel | grep -E "(kernload|kernbase|uscanner_devs)"

Rather than using the above tools plus popen() and some parsing code,
I have refactored src/usr.bin/elfdump/elfdump.c ,
making the main routine externally callable, returning the
desired info in a struct rather than print them out.

I don't know if/how other programs might need to call elfdump(),
but given that the changes I made have no functional or performance
drawback, I would like to commit them to the tree.
Objections ?

(note, the diff will be large because in the process I also removed
global variables and staticize/constify things)

	cheers
	luigi