mapping: define NOMINMAX to prevent breakage for foo::max()

sys_clock::time_point::max() is now used and without NOMINMAX, max
is defined as a macro in a common Windows header.

This commit defines NOMINMAX in the CMakeLists.txt and removes some
commented code in mapping.cpp.

Gitlab: #41
Change-Id: I98654cbafd362417d61734c4389b11ed68ff8dd8
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2d8e0c7..64c1b6d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -131,7 +131,9 @@
         -DMSGPACK_DISABLE_LEGACY_NIL \
         -DMSGPACK_DISABLE_LEGACY_CONVERT \
         -DUNICODE \
-        -D_UNICODE")
+        -D_UNICODE \
+        -DNOMINMAX \
+        ")
 endif()
 
 if (DNC_SYSTEMD AND BUILD_TOOLS AND NOT MSVC)