sync with experimental r6979

source/libs/lua52/ChangeLog

source/libs/lua52/luaerror.test

source/libs/lua53/ChangeLog

source/libs/lua53/luaerror.test

source/libs/luajit/ChangeLog

source/libs/luajit/luajiterr.test

source/texk/web2c/luatexdir/am/luapplib.am

source/texk/web2c/luatexdir/font/luafont.c

source/texk/web2c/luatexdir/font/luatexfont.h

source/texk/web2c/luatexdir/font/pdfglyphtounicode-luatex.c

source/texk/web2c/luatexdir/font/pdfglyphtounicode-pdftex.c

...ce/texk/web2c/luatexdir/font/pdfglyphtounicode-readme.txt

source/texk/web2c/luatexdir/font/writecff.c

source/texk/web2c/luatexdir/font/writefont.c

source/texk/web2c/luatexdir/font/writet1.c

source/texk/web2c/luatexdir/image/image.h

source/texk/web2c/luatexdir/image/pdftoepdf.c

source/texk/web2c/luatexdir/image/writeimg.c

source/texk/web2c/luatexdir/lua/lcallbacklib.c

source/texk/web2c/luatexdir/lua/lepdflib.cc.orig