sign extend the result of wait_pid

Unix/PmCleanSystem.icl

@@ -417,7 +417,8 @@ Link linker winfun path
 		# (w_pid,status) = wait_pid linker_pid 0
 		| w_pid <> -1 && w_pid<>linker_pid
 			= abort "waitpid failed"	
-		# result = (status bitand 0xff00) >> 8
+		# result = status >> 8;
+		# result = (result bitand 127) - (result bitand 128); // 8 bit sign extend
 		# wtermsig = status bitand 0x7f
 		| wtermsig<>0
 			= abort "linker exited abnormally"
@@ -448,8 +449,9 @@ Link linker winfun path
 		# (w_pid,status) = wait_pid ld_pid 0
 		| w_pid <> -1 && w_pid<>ld_pid
 			= abort "waitpid failed"	
-		# result = (status bitand 0xff00) >> 8
 		# wtermsig = status bitand 0x7f
+		# result = status >> 8;
+		# result = (result bitand 127) - (result bitand 128); // 8 bit sign extend
 		| wtermsig<>0
 			= abort "ld exited abnormally"
 		# link_ok = result>=0
@@ -493,7 +495,8 @@ Link linker winfun path
 		# (w_pid,status) = wait_pid linker_pid 0
 		| w_pid <> -1 && w_pid<>linker_pid
 			= abort "waitpid failed"	
-		# result = (status bitand 0xff00) >> 8
+		# result = status >> 8;
+		# result = (result bitand 127) - (result bitand 128); // 8 bit sign extend
 		# wtermsig = status bitand 0x7f
 		| wtermsig<>0
 			= abort "linker exited abnormally"