Enforce minimum supported libsqlite version

The server now checks the libsqlite both at compile time and on server
startup. The version the executable was built with and the one it's
running with may be different, so long as they're both at or above the
minimum supported version. One or both version numbers are printed on
startup, depending on if they're identical or not.

The compile-time ("Built with") version depends on the sqlite3.h header
used during compilation, while the runtime ("Using") version depends on
either:

* The sqlite3.c version used during compilation, if statically linked.
  (Which may be different from the header version and still compile and run
  fine.)
* The version of the libsqlite3.so or sqlite3.dll that the server
  loaded, if dynamically linked. Version mismatches here are normal,
  especially on Unix systems with their own system libraries.

The current minimum version is 3.33.0, from 2020-08-14, as that's the
one that introduced the UPDATE-FROM syntax used during login by
Database::updateSelectedByPlayerId().

Also rearranged the prints and initialization calls in main() slightly.

src/db/init.cpp

@@ -236,7 +236,20 @@ static int getTableSize(std::string tableName) {
     return result;
 }
 
+void Database::init() {
+    std::cout << "[INFO] Built with libsqlite " SQLITE_VERSION << std::endl;
+
+    if (sqlite3_libversion_number() != SQLITE_VERSION_NUMBER)
+        std::cout << "[INFO] Using libsqlite " << std::string(sqlite3_libversion()) << std::endl;
+
+    if (sqlite3_libversion_number() < MIN_SUPPORTED_SQLITE_NUMBER) {
+        std::cerr << "[FATAL] Runtime sqlite version too old. Minimum compatible version: " MIN_SUPPORTED_SQLITE << std::endl;
+        exit(1);
+    }
+}
+
 void Database::open() {
+
     // XXX: move locks here
     int rc = sqlite3_open(settings::DBPATH.c_str(), &db);
     if (rc != SQLITE_OK) {