Use C11 if possible

src/.clang-tidy

@@ -4,6 +4,7 @@ Checks: >
   -*-uppercase-literal-suffix,
   -bugprone-branch-clone,
   -bugprone-suspicious-string-compare,
+  -clang-analyzer-security.insecureAPI.DeprecatedOrUnsafeBufferHandling,
   -google-readability-todo,
   -hicpp-signed-bitwise,
   -llvm-header-guard,

test/.clang-tidy

@@ -4,6 +4,7 @@ Checks: >
   -*-uppercase-literal-suffix,
   -android-cloexec-fopen,
   -clang-analyzer-nullability.NullabilityBase,
+  -clang-analyzer-security.insecureAPI.DeprecatedOrUnsafeBufferHandling,
   -hicpp-signed-bitwise,
 WarningsAsErrors: '*'
 HeaderFilterRegex: '.*'

wscript

@@ -42,7 +42,9 @@ def options(ctx):
 def configure(conf):
     conf.load('compiler_c', cache=True)
     conf.load('autowaf', cache=True)
-    autowaf.set_c_lang(conf, 'c99')
+
+    if not autowaf.set_c_lang(conf, 'c11', mandatory=False):
+        autowaf.set_c_lang(conf, 'c99')
 
     if Options.options.strict:
         # Check for programs used by lint target