chore: upgrade c++ version to c++17

Author: theidexisted

CMakeLists.txt

@@ -161,7 +161,7 @@ endif(MSVC)
 
 # set a few other things at the top level to prevent incompatibilities
 set(CMAKE_C_STANDARD 99)
-set(CMAKE_CXX_STANDARD 11)
+set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF)
 add_definitions(-D_GNU_SOURCE)

src/tests/CMakeLists.txt

@@ -78,8 +78,8 @@ if (CRYPTO_BACKEND_LOWERCASE STREQUAL "openssl")
   find_package(OpenSSL 1.1.1 REQUIRED)
 endif()
 
-if(NOT CMAKE_CXX_COMPILER_ID STREQUAL "GNU" OR CMAKE_CXX_COMPILER_VERSION VERSION_GREATER "4.8.5")
-  set(CMAKE_CXX_STANDARD 14)
+if(NOT CMAKE_CXX_COMPILER_ID STREQUAL "GNU" OR CMAKE_CXX_COMPILER_VERSION VERSION_GREATER "7.0.0")
+  set(CMAKE_CXX_STANDARD 17)
 endif()
 
 if(CRYPTO_BACKEND_BOTAN3)