start reworking context references and smtp, imap

src/dc_keyhistory.rs

@@ -5,8 +5,8 @@ use crate::types::*;
 
 /* yes: uppercase */
 /* library private: key-history */
-pub unsafe fn dc_add_to_keyhistory(
-    _context: *mut dc_context_t,
+pub fn dc_add_to_keyhistory(
+    _context: &dc_context_t,
     _rfc724_mid: *const libc::c_char,
     _sending_time: time_t,
     _addr: *const libc::c_char,