Move helpers to a dedicated directory. The m4 dir might be there, too

helpers/constcheck.sh

@@ -0,0 +1,18 @@
+#! /bin/sh
+
+CT='ct.c'
+
+echo '#include <assert.h>' > "$CT"
+echo '#include <sodium.h>' >> "$CT"
+echo 'int main(void) {' >> "$CT"
+for macro in $(egrep -r '#define crypto_.*BYTES ' src/libsodium/include | \
+               cut -d: -f2- | cut -d' ' -f2 | \
+               fgrep -v edwards25519sha512batch | sort -u); do
+  func=$(echo "$macro" | tr A-Z a-z)
+  echo "  assert($func() == $macro);" >> "$CT"
+done
+echo "return 0; }" >> "$CT"
+
+cc -Wno-deprecated-declarations "$CT" -lsodium && ./a.out
+rm -f a.out "$CT"
+