check for one-to-one section-symbol relationship

There are cases in which the compiler will create symbols with NOTYPE
that map to a non-zero offset inside an .rodata section.  In that case, there
may not be a one-to-one relationship between that symbol and section as
the section may contains the data for multiple NOTYPE symbols.

This commit checks for this case and does not assign the symbol pointer of the
section that contains its data to avoid multiple symbols referring to the same
section from overwriting one another.  It also adds a check ensuring that all
symbols whose type is !NOTYPE start at offset 0 within the section.  This
should be guarenteed by the -ffunction-sections and -fdata-sections options
compiler options.

Signed-off-by: Seth Jennings <sjenning@redhat.com>
don't compare data on NOBITS sections

NOBITS section may have a non-zero size, however, the have no data and
the data descriptor will have d_buf set to NULL.

This commit fixes as segfault that occurs from trying to compare the
data of such sections.

Signed-off-by: Seth Jennings <sjenning@redhat.com>
Merge pull request #5 from spartacus06/fixes

Fixes