Improve safety of macOS available RAM calcuations at suggestion of Ansariel and Beq (#2423)

Author: brad-linden

indra/llcommon/llmemory.cpp

@@ -129,7 +129,7 @@ void LLMemory::updateMemoryInfo()
     {
         // Our Windows definition of PagefileUsage is documented by Microsoft as "the total amount of
         // memory that the memory manager has committed for a running process", which is rss.
-        sAllocatedPageSizeInKB = U32Bytes(info.resident_size);
+        sAllocatedPageSizeInKB = U32Kilobytes::convert(U64Bytes(info.resident_size));
 
         // Activity Monitor => Inspect Process => Real Memory Size appears to report resident_size
         // Activity monitor => main window memory column appears to report phys_footprint, which spot checks as at least 30% less.
@@ -139,7 +139,7 @@ void LLMemory::updateMemoryInfo()
         // reported for the app by the Memory Monitor in Instruments.' It is still about 8% bigger than phys_footprint.
         //
         // (On Windows, we use WorkingSetSize.)
-        sAllocatedMemInKB = U32Bytes(info.resident_size - info.reusable);
+        sAllocatedMemInKB = U32Kilobytes::convert(U64Bytes(info.resident_size - info.reusable));
      }
     else
     {