docs: avoid using colon character inside arguments of @pxref Fixes automake bug#9753 * doc/automake.texi (VPATH Builds): Avoid using colon character `:' inside arguments of @pxref, as this can cause problems in the generated `.info' files, and such an usage will be explicitly forbidden by future texinfo documentation. * THANKS: Update. Reported by Дилян Палаузов.