Make ShmInfo track the *requested* size

On macOS, the size of the allocated shared memory block might not
precisely match the request. But it needs to be at least as large as
the requested size. E.g.: sizes less than 16384 round up to 16384.

When asking the SharedMemory object for its size, we should remember the
requested size and return that value, rather than the rounded up one.

src/main/java/org/apposed/appose/shm/ShmBase.java

@@ -116,6 +116,9 @@ protected static class ShmInfo<HANDLE> {
 		/** Size in bytes. */
 		int size;
 
+		/** Size in bytes allocated by the operating system. */
+		int totalSize;
+
 		/** Pointer referencing the shared memory. */
 		Pointer pointer;
 

src/main/java/org/apposed/appose/shm/ShmLinux.java

@@ -119,7 +119,8 @@ private static ShmInfo<Integer> prepareShm(String name, boolean create, int size
 			}
 
 			ShmInfo<Integer> info = new ShmInfo<>();
-			info.size = shm_size;
+			info.size = size;
+			info.totalSize = shm_size;
 			info.name = withoutLeadingSlash(shm_name);
 			info.pointer = pointer;
 			info.handle = shmFd;

src/main/java/org/apposed/appose/shm/ShmMacOS.java

@@ -110,7 +110,8 @@ private static ShmInfo<Integer> prepareShm(String name, boolean create, int size
 			}
 
 			ShmInfo<Integer> info = new ShmInfo<>();
-			info.size = shm_size;
+			info.size = size;
+			info.totalSize = shm_size;
 			info.name = withoutLeadingSlash(shm_name);
 			info.pointer = pointer;
 			info.handle = shmFd;

src/main/java/org/apposed/appose/shm/ShmWindows.java

@@ -122,7 +122,8 @@ private static ShmInfo<WinNT.HANDLE> prepareShm(String name, boolean create, int
 			}
 
 			ShmInfo<WinNT.HANDLE> info = new ShmInfo<>();
-			info.size = shm_size;
+			info.size = size;
+			info.totalSize = shm_size;
 			info.name = shm_name;
 			info.pointer = pointer;
 			info.writePointer = writePointer;