First set of changes to include estream into the API.
* configure.ac (AH_BOTTOM): Define GPGRT_ENABLE_ES_MACROS. * src/gpg-error.h.in: include stdio.h. Include most of the estream functions and rename structures and types. * src/estream.h: Rewrite. Include only gpg-error.h and local prototypes. * src/estream.c: Rename types and macros. * src/estream-printf.c (_gpgrt_estream_snprintf): Prefix public functions with _gpgrt_.