MDEV-15091 : Windows, 64bit: reenable and fix warning C4267 (conversion from 'size_t' to 'type', possible loss of data)

Handle string length as size_t, consistently (almost always:))
Change function prototypes to accept size_t, where in the past
ulong or uint were used. change local/member variables to size_t
when appropriate.

This fix excludes rocksdb, spider,spider, sphinx and connect for now.

tests/mysql_client_test.c

@@ -31,6 +31,9 @@
   The fw.c file includes all the mysql_client_test framework; this file
   contains only the actual tests, plus the list of test functions to call.
 */
+#ifdef _MSC_VER
+#pragma warning (disable : 4267)
+#endif
 
 #include "mysql_client_fw.c"
 #ifndef _WIN32