JSONIPC: jsonipc.hh: always use `static inline` except where ODR applies
JSONIPC: jsonipc.hh: always use `static inline` except where ODR applies

Generally, use `static inline` to avoid useless linker emission of unused free
standing functions. Except for functions that define `static` variables, these
need to be emitted for global linkage (via `extern inline` aka `inline`), so
the linker can apply the One-Definition-Rule to produce a single global symbol.

Signed-off-by: Tim Janik <6ec6ff229c4e1c5bbd5933ee92e6c5832ff023bb@gnu.org>

swesterfeld/beast,swesterfeld/beast,tim-janik/beast,tim-janik/beast,swesterfeld/beast,tim-janik/beast,swesterfeld/beast,tim-janik/beast,swesterfeld/beast,tim-janik/beast,tim-janik/beast,tim-janik/beast,swesterfeld/beast,swesterfeld/beast