[LyX/master] boost, cmake: Turn off warning that signals are deprecated

[Kornel Benko]

commit 21541a07de371b09b3ec6e89e52b45ea224767e8
Author: Kornel Benko <kor...@lyx.org>
Date:   Tue Apr 29 18:01:50 2014 +0200

    boost, cmake: Turn off warning that signals are deprecated

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 51b67fb..8ab1bea 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -590,6 +590,7 @@ else()
                set(Lyx_Boost_Libraries boost_signals boost_regex)
        endif()
        add_definitions(-DBOOST_USER_CONFIG="<config.h>")
+       add_definitions(-DBOOST_SIGNALS_NO_DEPRECATION_WARNING=1)
        include_directories(${TOP_SRC_DIR}/boost)
        add_subdirectory(boost "${TOP_BINARY_DIR}/boost")
 endif()