support incremental matching
@chpe
Submitted by Christian Persch Link to original bug (#689794)
Description
Suppose you have a large piece of data you want to match with a regex; so much you can't fit it into memory all at once. So you want to load slices of it and match that. The problem there is that a match may only be partial at the end of the available data. Then you retrieve its position (the first inspected character), and use the max lookbehind length to know how much data you need to keep from the this data slice to possibly complete the match with the next data slice.
For this to work, we need API to a) retrieve the max lookbehind of a pattern (PCRE_INFO_MAXLOOKBEHIND), and b) to retrieve the position of the partial match, which the current GMatchInfo doesn't allow.
See man:pcrepartial(3) for more information on incremental (there called 'multi-segmented') matching.