CLEANUP: sample: rename sample_conv_var2smp() to *_sint

This one only handles integers, contrary to its sibling with the suffix
_str that only handles strings. Let's rename it and uninline it since it
may well be used from outside.

(cherry picked from commit d9be59952975e679f3305e32620ae3572a6a952c)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/include/haproxy/sample.h b/include/haproxy/sample.h
index aac6efa..e1d0a86 100644
--- a/include/haproxy/sample.h
+++ b/include/haproxy/sample.h
@@ -40,6 +40,7 @@
 struct sample *sample_fetch_as_type(struct proxy *px, struct session *sess,
                                    struct stream *strm, unsigned int opt,
                                    struct sample_expr *expr, int smp_type);
+int sample_conv_var2smp_sint(const struct arg *arg, struct sample *smp);
 void release_sample_expr(struct sample_expr *expr);
 void sample_register_fetches(struct sample_fetch_kw_list *psl);
 void sample_register_convs(struct sample_conv_kw_list *psl);