patch 9.1.1467: too many strlen() calls

Problem:  too many strlen() calls
Solution: Change expand_env() to return string length
          (John Marriott)

This commit does the following changes:
- In expand_env_esc():
  - return the length of the returned dst string.
  - refactor to remove some calls to STRLEN() and STRCAT()
  - add check for out-of-memory condition.
- Change call sites in various source files to use the return value

closes: #17561

Signed-off-by: John Marriott <basilisk@internode.on.net>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/version.c b/src/version.c
index 0b6a3b0..168ff4e 100644
--- a/src/version.c
+++ b/src/version.c
@@ -710,6 +710,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1467,
+/**/
     1466,
 /**/
     1465,