patch 8.2.2020: some compilers do not like the "namespace" argument

Problem:    Some compilers do not like the "namespace" argument.
Solution:   Rename to "use_namespace". (closes #7332)
diff --git a/src/proto/vim9compile.pro b/src/proto/vim9compile.pro
index 9ed86da..a19088b 100644
--- a/src/proto/vim9compile.pro
+++ b/src/proto/vim9compile.pro
@@ -8,7 +8,7 @@
 int vim9_comment_start(char_u *p);
 char_u *peek_next_line_from_context(cctx_T *cctx);
 char_u *next_line_from_context(cctx_T *cctx, int skip_comment);
-char_u *to_name_end(char_u *arg, int namespace);
+char_u *to_name_end(char_u *arg, int use_namespace);
 char_u *to_name_const_end(char_u *arg);
 exptype_T get_compare_type(char_u *p, int *len, int *type_is);
 void error_white_both(char_u *op, int len);