- Explain clearly why a different firmware is being installed (if/when
  it is being installed).  Improve other error messages while here.

- Select special FPGA specific configuration profile when appropriate.

MFC after:	3 days
Add sbuf_start_section() and sbuf_end_section() functions, which can
be used for automatic section alignment.

Discussed with:	kib
Reviewed by:	kib
MFC after:	1 month
Add sbuf_start_section and sbuf_end_section to the libsbuf symbol map.

MFC after:	1 month
Document sbuf_start_section() and sbuf_end_section() functions.

MFC after:	1 month
Spelling correction