Modernise use of AC_CHECK_TYPE

Modernise use of AC_CHECK_TYPE

Prior to autoconf 2.13, AC_CHECK_TYPE took two arguments, the type
to check and the a default type to use if that type wasn't defined.
This usage has been deprecated since 2.13, and the AC_CHECK_TYPE
macro itself now behaves differently. Whilst there is a compatibility
mode, the autoconf documentation discourages its use.

We also have an occurence of a slightly more modern AC_CHECK_TYPE,
where we explicitly #define a default value if one isn't provided.
The autoconf manual also discourages this form, however, in favour
of using AC_CHECK_TYPES, and placing suitable typedefs in an
external header file.

Modify our code so we do things in the recommended way.

Change-Id: Ie28067f2c90e9a3aa25cfde45ef081da2d380ee1
Reviewed-on: http://gerrit.openafs.org/1914
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>