warnings when parsing GCF files

[sillitoe]

Encountered two different warnings on chains 5yu3D and 5xg3B

CHOPPING 72 [5yu3D] <Chopping id=5yu3D01 '3-116,305-328'> ...
pdb_aa 'P' does not match seqres_aa '*' (line: 346)
caught exception when parsing GCF (skipping): invalid literal for int() with base 10: '*'

CHOPPING 89 [5xg3B] <Chopping id=5xg3B00 '2-1177'> ...
pdb_aa 'L' does not match seqres_aa 'D' (line: 316)