patch: support for patches without dates and generated with -U1; shrink

patch: support for patches without dates and generated with -U1; shrink

function                                             old     new   delta
extract_filename                                       -      92     +92
extract_filename_and_free_line                        70       -     -70
patch_main                                          1096    1009     -87
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(add/remove: 1/1 grow/shrink: 0/1 up/down: 92/-157)           Total: -65 bytes