wrong comment in libpq.h

Hi Hackers,

There is a comment like below in src/include/libpq/libpq.h,

 /*
  * prototypes for functions in be-secure.c
  */
extern PGDLLIMPORT char *ssl_library;
extern PGDLLIMPORT char *ssl_cert_file;

...

However, 'ssl_library', 'ssl_cert_file' and the rest are global
parameter settings, not functions. To address this confusion, it would
be better to move all global configuration settings to the proper
section, such as /* GUCs */, to maintain consistency.

I have attached an attempt to help address this issue.

Thank you,

David