Merge branch 'fix-timestamps' into check-tex-timestamps

We need the fixed timestamp comparison code to correctly compare timestamps of tex files.
psfragfig also processes the graphic if the tex file wit psfrag commands is newer than the pdf.
Avoid errors because \pstool@tex is undefined when called via \pstool.
Simplify timestamp comparison for tex files (filemodCmp correctly handles empty arguments and non-existent files).
fix the = to # substitution
Pull in changes from upstream.
support cross referencing. nice.

also update the example a bit so it's a little more explanatory
Also check pull in psfrag macros from a directory-wide psfrag.tex file.
A couple of small cosmetic changes.
update readme
waste some time writing some code to nicely typeset .sty files

works, mostly
lots of edge cases
should be better for expl3 code
not sure how much time to spend on it!
Fixed the inclusion of directory wide psfrag.tex.
Pull in some changes from the check-tex-timestamps branch
update example for forthcoming new feature to be committed
update the read me
add some extra line breaks in the written .tex file

easier to parse visually if necessary
add [macro-file=] feature and checking for .tex file changes
update docs
Pull in new upstream changes.