Disable exceptions in Microsoft STL (#715)

This is the copy of patch proposed to LLVM's copy of benchmark via
https://reviews.llvm.org/D52998.

Author: kirillbobyrev

CMakeLists.txt

@@ -103,6 +103,7 @@ if (MSVC)
   if (NOT BENCHMARK_ENABLE_EXCEPTIONS)
     add_cxx_compiler_flag(-EHs-)
     add_cxx_compiler_flag(-EHa-)
+    add_definitions(-D_HAS_EXCEPTIONS=0)
   endif()
   # Link time optimisation
   if (BENCHMARK_ENABLE_LTO)
@@ -167,7 +168,7 @@ else()
   endif()
   # ICC17u2: overloaded virtual function "benchmark::Fixture::SetUp" is only partially overridden
   # (because of deprecated overload)
-  add_cxx_compiler_flag(-wd654)  
+  add_cxx_compiler_flag(-wd654)
   add_cxx_compiler_flag(-Wthread-safety)
   if (HAVE_CXX_FLAG_WTHREAD_SAFETY)
     cxx_feature_check(THREAD_SAFETY_ATTRIBUTES)