Make sure we get C99
The compiler might default to something older, so make sure we get
the features we need.
diff --git a/CMakeLists.txt b/CMakeLists.txt
index ca1e85b..a63288a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -68,6 +68,9 @@
set(CMAKE_C_FLAGS_MINSIZEREL "${CMAKE_C_FLAGS_MINSIZEREL} -UNDEBUG")
set(CMAKE_CXX_FLAGS_MINSIZEREL "${CMAKE_CXX_FLAGS_MINSIZEREL} -UNDEBUG")
+# Make sure we get a sane C version
+set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -std=gnu99")
+
# Tell the compiler to be stringent
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall -Wformat=2")
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wformat=2")