* boot-9.scm (load-module): Support an optional custom reader arg,
implemented by passing on to r4rs's load.
* r4rs.scm (load): Support an optional custom reader arg,
implemented by passing on to primitive-load.
* load.c (the_reader, the_reader_fluid_num): New.
(scm_primitive_load): Support custom reader.
(scm_init_load): Init the_reader and the_reader_fluid_num; export
the_reader as `current-reader'.
* scheme-compound.texi: Renamed to api-compound.texi.
* scheme-control.texi: Renamed to api-control.texi.
* scheme-data.texi: Renamed to api-data.texi.
* scheme-debug.texi: Renamed to api-debug.texi.
* deprecated.texi: Renamed to api-deprecated.texi.
* scheme-evaluation.texi: Renamed to api-evaluation.texi.
* ref-init.texi: Renamed to api-init.texi.
* scheme-io.texi: Renamed to api-io.texi.
* scheme-memory.texi: Renamed to api-memory.texi.
* scheme-modules.texi: Renamed to api-modules.texi.
* scheme-options.texi: Renamed to api-options.texi.
* scm.texi: Renamed to api-overview.texi.
* scheme-procedures.texi: Renamed to api-procedures.texi.
* scheme-scheduling.texi: Renamed to api-scheduling.texi.
* scheme-scm.texi: Renamed to api-scm.texi.
* scheme-smobs.texi: Renamed to api-smobs.texi.
* scheme-snarf.texi: Renamed to api-snarf.texi.
* scheme-translation.texi: Renamed to api-translation.texi.
* scheme-utility.texi: Renamed to api-utility.texi.
* debugging.texi: Renamed to scheme-debugging.texi.
* scripts.texi: Renamed to scheme-scripts.texi.
* program.texi: Renamed to libguile-program.texi.