Fixed broken make on Linux etc because of missing os_timestamp_linux.c (was renamed to os_timestamp_posix.c)

git-svn-id: https://svn.pjsip.org/repos/pjproject/trunk@447 74dad513-b988-da41-8d7b-12977e46ad98
diff --git a/pjlib/build/os-linux.mak b/pjlib/build/os-linux.mak
index 7a30fa7..11c6fa7 100644
--- a/pjlib/build/os-linux.mak
+++ b/pjlib/build/os-linux.mak
@@ -11,7 +11,7 @@
 			file_io_ansi.o guid_simple.o \
 			log_writer_stdout.o os_core_unix.o \
 			os_error_unix.o os_time_unix.o \
-			os_timestamp_common.o os_timestamp_linux.o \
+			os_timestamp_common.o os_timestamp_posix.o \
 			pool_policy_malloc.o sock_bsd.o sock_select.o
 
 ifeq (epoll,$(LINUX_POLL))