help.c: use SHELL_PATH instead of hard-coded "/bin/sh"

diff --git a/RelNotes b/RelNotes
index 2bff7b20de8972e2a8cf9bf7a8cea4ff2e9789f1..689db12994adff4279d335ff75207026f1fdd8ec 120000 (symlink)
--- a/RelNotes
+++ b/RelNotes
@@ -1 +1 @@
-Documentation/RelNotes/1.9.4.txt
\ No newline at end of file
+Documentation/RelNotes/2.3.2.txt
\ No newline at end of file