Fix two problems:
- The value of mysqli_get_client_info() has been changed recently and did
not include "mysqlnd" anymore thus the test suite was thinking the build
is always libmysql. This did not kept the suite from running pconn tests
- Going back to the libc allocator because the memory arena could be on a
persistent connections. If the build is not debug there will be no error
but the memory will be freed and in the second use of this pconn freed
memory will be used - not good! For now the arena doesn't take an argument
whether it should allocate persistently or not, thus persistent is safe
for now.
Johannes gave his +1 to commit this.
Hardwire function call instead of using callbacks. We don't actually need
callbacks, it was done for making 2 functions static, not to pollute the
global functions space but that had its price of 8 bytes overheat per
allocation, which is just too much. Also making the app member 32b instead
of 64b, which should save additional 4 byte, to the total of 12 byte per
allocation of a row buffer.
