check:proc-ec is unbound

[diamond-lizard]

When running this test from SRFI-78's examples:

(check-ec (:range e 100)
          (:let x (expt 2.0 e))
          (= (+ x 1) x) => #f (e x))

I get:

Error: unbound variable: check:proc-ec

        Call history:

        <syntax>          (##core#if #t (and433 (not164 stop125)) #f)
        <syntax>          (and433 (not164 stop125))
        <syntax>          (not164 stop125)
        <syntax>          (loop169 (|+160| e 1))
        <syntax>          (|+160| e 1)
        <syntax>          (##core#undefined)
        <syntax>          (##core#undefined)
        <syntax>          (##core#let () loop169)
        <syntax>          (##core#begin loop169)
        <syntax>          (##core#undefined)
        <syntax>          (##core#undefined)
        <eval>    (>=78 check:mode79 1)
        <eval>    (check:proc80 (quote81 (+ 1 1)) (lambda82 () (+ 1 1)) equal?75 2)
        <eval>    (+ 1 1)
        <eval>    (>=91 check:mode92 1)
        <eval>    (check:proc-ec93 (let94 ((cases95 0)) (let94 ((w96 (first-ec97 #f (nested84 (|:range| e 100) (|:let|...       <--

This is the same problem as in issue 7, only with check:proc-ec.

The fix should be the same too: (export (check check:proc-ec))