Make _pushPopGS vastly more efficient

Don't re-parse the entire content stream just to add some pre/post ops.
Just write the pre-post ops directly, with the original content in
between.

Version 1.26.0 update

Don't call _pushPopGS() when merging pages.

It re-parses the content stream per page, which is slow, memory hungry, and not needed
for our use-case.

Conform to semantic versioning. Patch number added

Version 1.25

Version 1.24

Version 1.23

Version 1.22

Version 1.21

Version 1.20