Do not export variables with dot names (re: 8e72608c)

Variables with a dot in their name, such as those declared in
namespace { ... } blocks, are usually stored in a separate tree
with their actual names not containing any dots. But under some
circumstances, including at least direct assignment of a
non-preexisting dot variable, dot variables are stored in the main
sh.var_tree with names actually containing dots. With allexport
active, those could end up exported to the environment. This bug
was also present in previous release versions of ksh.

src/cmd/ksh93/sh/name.c: pushnam():
- Check for a dot in the name before pushing a variable to export.

NEWS

@@ -3,6 +3,14 @@ For full details, see the git log at: https://github.com/ksh93/ksh/tree/1.0
 
 Any uppercase BUG_* names are modernish shell bug IDs.
 
+2022-02-05:
+
+- Fixed: the -a/--allexport shell option incorrectly exported some variables
+  with names containing a dot to the environment. Note that the '-x' typeset
+  attribute may still be set for them, but this will now not have any
+  effect. Variables created in namespaces declared with the 'namespace'
+  keyword are only exported while their namespace is active.
+
 2022-02-04:
 
 - Fixed a bug in 'typeset -p': for an indexed array variable that is set