perf tools: Rewrite and improve support for kernel modules

Representing modules as struct map entries, backed by a DSO, etc,
using /proc/modules to find where the module is loaded.

DSOs now can have a short and long name, so that in verbose mode we
can show exactly which .ko or vmlinux image was used.

As kernel modules now are a DSO separate from the kernel, we can
ask for just the hits for a particular set of kernel modules, just
like we can do with shared libraries:

[root@doppio linux-2.6-tip]# perf report -n --vmlinux
/home/acme/git/build/tip-recvmmsg/vmlinux --modules --dsos \[drm\] | head -15
    84.58%      13266             Xorg  [k] drm_clflush_pages
     4.02%        630             Xorg  [k] trace_kmalloc.clone.0
     3.95%        619             Xorg  [k] drm_ioctl
     2.07%        324             Xorg  [k] drm_addbufs
     1.68%        263             Xorg  [k] drm_gem_close_ioctl
     0.77%        120             Xorg  [k] drm_setmaster_ioctl
     0.70%        110             Xorg  [k] drm_lastclose
     0.68%        106             Xorg  [k] drm_open
     0.54%         85             Xorg  [k] drm_mm_search_free
[root@doppio linux-2.6-tip]#

Specifying --dsos /lib/modules/2.6.31-tip/kernel/drivers/gpu/drm/drm.ko
would have the same effect. Allowing specifying just 'drm.ko' is left
for another patch.

Processing kallsyms so that per kernel module struct map are
instantiated was also left for another patch. That will allow
removing the module name from each of its symbols.

struct symbol was reduced by removing the ->module backpointer and
moving it (well now the map) to struct symbol_entry in perf top,
that is its only user right now.

The total linecount went down by ~500 lines.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Avi Kivity <avi@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>