Dep: Raise required boost versions to 1.73 on windows and 1.71 on linux and remove compatibility code for unsupported versions

# Conflicts:
#	dep/boost/CMakeLists.txt

dep/boost/CMakeLists.txt

@@ -37,9 +37,9 @@ check_cxx_source_compiles("
 
 if (WIN32)
   # On windows the requirements are higher according to the wiki.
-  set(BOOST_REQUIRED_VERSION 1.70)
+  set(BOOST_REQUIRED_VERSION 1.73)
 else()
-  set(BOOST_REQUIRED_VERSION 1.68)
+  set(BOOST_REQUIRED_VERSION 1.71)
 endif()
 
 if (STD_HAS_WORKING_WREGEX)