bitbake.conf: Add filename and lineno to BB_SIGNATURE_EXCLUDE_FLAGS

bitbake.conf: Add filename and lineno to BB_SIGNATURE_EXCLUDE_FLAGS

This is mainly a performance optimisation. Since we added these flags
to functions, the system spends a lot of time trying to expand these
flags. The values don't really influence checksums and don't need to
be included since if the function content changes, that is will be
detected regardless and is the key detail we care about.

Therefore exclude these from the checksums and gain a signficiant
chunk of parsing speed back.

(From OE-Core rev: 2a1edfd9cfa16ec334c0758b47677d4fee5e79a8)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>