Fix compiler warnings on 64-bit Windows

GCC reports various instances of

     warning: cast to pointer from integer of different size 
[-Wint-to-pointer-cast]
     warning: cast from pointer to integer of different size 
[-Wpointer-to-int-cast]

and MSVC equivalently

     warning C4312: 'type cast': conversion from 'int' to 'void *' of 
greater size
     warning C4311: 'type cast': pointer truncation from 'void *' to 'long'

in ECPG test files.  This is because void* and long are cast back and
forth, but on 64-bit Windows, these have different sizes.  Fix by
using intptr_t instead.

The code actually worked fine because the integer values in use are
all small.  So this is just to get the test code to compile warning-free.

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services