svn:ignore for in-tree builds

source/.gitignore

source/libs/.gitignore

source/libs/dummy/.gitignore

source/libs/libpng/.gitignore

source/libs/obsdcompat/.gitignore

source/libs/obsdcompat/obsdcompat/.gitignore

source/libs/xpdf/.gitignore

source/libs/xpdf/fofi/.gitignore

source/libs/xpdf/goo/.gitignore

source/libs/xpdf/xpdf/.gitignore

source/libs/zlib/.gitignore

source/texk/.gitignore

source/texk/dummy/.gitignore

source/texk/kpathsea/.gitignore

source/texk/kpathsea/doc/.gitignore

source/texk/kpathsea/man/.gitignore

source/texk/web2c/.gitignore

source/texk/web2c/doc/.gitignore

source/texk/web2c/lib/.gitignore

source/texk/web2c/luatexdir/.gitignore