CMakeLists.txt: silence warnings about always-true comparisons (generated by Clang 3.2)

CMakeLists.txt

@@ -132,7 +132,8 @@ else ()
     add_definitions(-std=gnu99 -Wall -Wno-unused-value -Wno-parentheses -Wno-switch -Wredundant-decls)
 
     if (NOT CMAKE_C_COMPILER_ID STREQUAL "PathScale")
-        add_definitions(-Werror=implicit-function-declaration -Wno-switch-enum -Wno-unused-function)
+        add_definitions(-Werror=implicit-function-declaration -Wno-switch-enum -Wno-unused-function
+                        -Wno-tautological-constant-out-of-range-compare)
     endif ()
     
     if (CMAKE_C_COMPILER_ID MATCHES "^Clang")