Fix TestProcessAPI.py to only allocate sys.maxsize buffer

I hardcoded nearly a UINT64_MAX number in this test case,
and python is not able to convert it to a long on some
platforms.  Use sys.maxsize instead; this also would have
failed if the testsuite was run on a 32-bit system.

lldb/test/API/python_api/process/TestProcessAPI.py

@@ -3,6 +3,7 @@ Test SBProcess APIs, including ReadMemory(), WriteMemory(), and others.
 """
 
 import lldb
+import sys
 from lldbsuite.test.decorators import *
 from lldbsuite.test.lldbtest import *
 from lldbsuite.test.lldbutil import get_stopped_thread, state_type_to_str
@@ -76,15 +77,16 @@ class ProcessAPITestCase(TestBase):
         # will try to malloc it and fail, we should get an error 
         # result.
         error = lldb.SBError()
+        bigsize = sys.maxsize - 8;
         content = process.ReadMemory(
                 val.AddressOf().GetValueAsUnsigned(), 
-                0xffffffffffffffe8, error)
+                bigsize, error)
         if error.Success():
             self.assertFalse(error.Success(), "SBProcessReadMemory claims to have "
-                      "successfully read 0xffffffffffffffe8 bytes")
+                      "successfully read 0x%x bytes" % bigsize)
         if self.TraceOn():
-            print("Tried to read 0xffffffffffffffe8 bytes, got error message: ",
-                  error.GetCString())
+            print("Tried to read 0x%x bytes, got error message: %s" %
+                  (bigsize, error.GetCString()))
 
         # Read (char *)my_char_ptr.
         val = frame.FindValue("my_char_ptr", lldb.eValueTypeVariableGlobal)