[PATCH] Doc: Correct recurring typo in documentation and add a check.

[John Darrington]

Change "Lets" to "Let's" and add a syntax-check test so this
problem won't keep comming back.
---
 cfg.mk        | 8 ++++++++
 doc/poke.texi | 2 +-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/cfg.mk b/cfg.mk
index 3e28dacc..0dcd00d5 100644
--- a/cfg.mk
+++ b/cfg.mk
@@ -6,3 +6,11 @@ export _gl_TS_headers = *.h
 local-checks-to-skip =                  \
    sc_tight_scope \
    sc_prohibit_gnu_make_extensions
+
+sc_jemarchism.z:
+       @prohibit='(^|[ ])[Ll]ets( |$$)'                                \
+       in_vc_files='$(texinfo_suffix_re_)'                             \
+       halt='found use of "lets" in Texinfo source'                    \
+         $(_sc_search_regexp)
+
+local-checks-available=sc_jemarchism
diff --git a/doc/poke.texi b/doc/poke.texi
index 56fd0f6b..4fdd4b7c 100644
--- a/doc/poke.texi
+++ b/doc/poke.texi
@@ -3752,7 +3752,7 @@ by adding a load command to our @code{.pokerc}.  For 
example:
 
 @subsection Heterogeneous Related Data
 
-Lets recap the structure of the header of a Stupid Bitmap:
+Let's recap the structure of the header of a Stupid Bitmap:
 
 @example
                 SBM header
-- 
2.20.1