* README (Requirements): Remove "optional" verbiage.
* doc/guix.texi (Requirements): Move Guile-JSON from optional to required.
* configure.ac (HAVE_GUILE_JSON): Remove Automake conditional.
(have_guile_json): Error if not "yes".
* Makefile.am (MODULE, SCM_TESTS)[HAVE_GUILE_JSON]: Add modules and tests
unconditionally.
* gnu/packages/package-mangement.scm (guix-minimal)[propagated-inputs]: Leave
guile-json input.