Split context access functions from util.c

The util.c file should contain internal utility functions, rather than
exported functions.

Signed-off-by: Petr Tesarik <ptesarik@suse.cz>
Move xen_p2m_mfn from ELF private data to common kdump_ctx

The map is needed for any Xen dump file format, not just ELF.

Signed-off-by: Petr Tesarik <ptesarik@suse.cz>
Sanity checks in process_xc_xen_note

Add some sanity checks for data found in Xen xc_core ELF note:

  - page size must be a power of 2
  - only dump core version 1 is supported

Signed-off-by: Petr Tesarik <ptesarik@suse.cz>
Free VMCOREINFO buffers in kdump_free()

These buffers are allocated by the library, so they must be freed again
after we're done.

Signed-off-by: Petr Tesarik <ptesarik@suse.cz>