doco scm_remember

[Kevin Ryde]

FYI,
        * deprecated.texi (Deprecated): Add scm_remember.


 - C Function: void scm_remember (SCM *ptr)
     Create a reference to the object at PTR, so it's certain to be
     present on the stack and hence won't be freed by the garbage
     collector.

     This function has been superceded by `scm_remember_upto_here_1'
     (which takes an object, not a pointer to one), *Note Remembering
     During Operations::.