[Minor] Minor portability fixes

CMakeLists.txt

@@ -24,8 +24,6 @@ SET(RSPAMD_VERSION         "${RSPAMD_VERSION_MAJOR}.${RSPAMD_VERSION_MINOR}")
 PROJECT(rspamd VERSION "${RSPAMD_VERSION}" LANGUAGES C CXX ASM)
 
 # This is supported merely with cmake 3.1
-SET(CMAKE_CXX_STANDARD 17)
-SET(CMAKE_CXX_STANDARD_REQUIRED ON)
 SET(USE_CXX_LINKER 1)
 
 SET(CMAKE_C_STANDARD 11)

config.h.in

@@ -376,8 +376,16 @@ typedef off_t goffset;
 # define NBYTES(nbits)   (((nbits) + BITSPERBYTE - 1) / BITSPERBYTE)
 #endif
 
+
+#ifdef  __cplusplus
+extern "C" {
+#endif
 extern uint64_t ottery_rand_uint64(void);
 #define UCL_RANDOM_FUNCTION ottery_rand_uint64()
+#ifdef  __cplusplus
+}
+#endif
+
 
 /* Disable slab allocator if jemalloc is already in the system */
 #if defined(WITH_JEMALLOC) || defined(__FreeBSD__) || \