gdb.base/coremaker2.c: Fix compilation problems for x86_64 -m32 multilib

There are compilation warnings / errors when compiling coremaker2.c
for the gdb.base/corefile2.exp tests.  Here's the command to use
on x86_64 linux:

make check RUNTESTFLAGS="--target_board unix/-m32" \
           TESTS="gdb.base/corefile2.exp"

These are the warnings / errors - I've shortened the paths somewhat:

gdb compile failed, gdb/testsuite/gdb.base/coremaker2.c: In function 'main':
gdb/testsuite/gdb.base/coremaker2.c:106:11: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
  106 |   addr = ((unsigned long long) buf_ro + pagesize) & ~(pagesize - 1);
      |           ^
gdb/testsuite/gdb.base/coremaker2.c:108:15: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
  108 |   if (addr <= (unsigned long long) buf_ro
      |               ^
gdb/testsuite/gdb.base/coremaker2.c:109:18: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
  109 |       || addr >= (unsigned long long) buf_ro + sizeof (buf_ro))
      |                  ^
gdb/testsuite/gdb.base/coremaker2.c:115:19: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
  115 |   mbuf_ro = mmap ((void *) addr, pagesize, PROT_READ,
      |                   ^
gdb/testsuite/gdb.base/coremaker2.c:130:11: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
  130 |   addr = ((unsigned long long) buf_rw + pagesize) & ~(pagesize - 1);
      |           ^
gdb/testsuite/gdb.base/coremaker2.c:132:15: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
  132 |   if (addr <= (unsigned long long) buf_rw
      |               ^
gdb/testsuite/gdb.base/coremaker2.c:133:18: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
  133 |       || addr >= (unsigned long long) buf_rw + sizeof (buf_rw))
      |                  ^
gdb/testsuite/gdb.base/coremaker2.c:139:19: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
  139 |   mbuf_rw = mmap ((void *) addr, pagesize, PROT_READ,
      |                   ^

These were fixed by changing unsigned long long to uintptr_t.

Tested on either rawhide or Fedora 32 with architectures: x86_64,
x86_64/-m32, aarch64, s390x, and ppc64le.

gdb/testsuite/ChangeLog:

	* gdb.base/coremaker2.c: Change all uses of 'unsigned long long'
	to 'uintptr_t'
	(inttypes.h): Include.