Remove dc_location_t

dc_location_t is an incomplete copy of _dc_location

The difference is that it lacks `int independent` field.
As a result, calloc did not allocate memory for this field.
deltachat-core (C version) has only one dc_location_t, that includes the last field.

src/context.rs

@@ -111,22 +111,6 @@ pub struct SmtpState {
     pub probe_network: i32,
 }
 
-// location handling
-#[derive(Copy, Clone)]
-#[repr(C)]
-pub struct _dc_location {
-    pub location_id: uint32_t,
-    pub latitude: libc::c_double,
-    pub longitude: libc::c_double,
-    pub accuracy: libc::c_double,
-    pub timestamp: i64,
-    pub contact_id: uint32_t,
-    pub msg_id: uint32_t,
-    pub chat_id: uint32_t,
-    pub marker: *mut libc::c_char,
-    pub independent: uint32_t,
-}
-
 // create/open/config/information
 pub fn dc_context_new(
     cb: Option<dc_callback_t>,