Add CMake project, GCC support (#540)

This is extract from #211 that enables compilation with GCC. With #211
now in the state of bitrot, I would rather try approaching it in smaller
steps that can be hopefully merged quicker, even if it does not provide
full support for all the features #211 provided.

This will _compile_ correctly with my (@janisozaur) GCC, but clang is
more picky about flexible array members and refuses to compile it yet.
I will extract remaining parts of #211 in future PRs.

I marked @fwcd as author, as he did most of the work in #211.

src/CalcManager/CEngine/CMakeLists.txt

@@ -0,0 +1,14 @@
+target_sources(CalcManager PRIVATE
+	calc.cpp
+	CalcInput.cpp
+	CalcUtils.cpp
+	History.cpp
+	Number.cpp
+	Rational.cpp
+	RationalMath.cpp
+	scicomm.cpp
+	scidisp.cpp
+	scifunc.cpp
+	scioper.cpp
+	sciset.cpp
+)

src/CalcManager/CEngine/Rational.cpp

@@ -1,6 +1,5 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 
-#include <intsafe.h>
 #include "Header Files/Rational.h"
 
 using namespace std;
@@ -53,8 +52,8 @@ namespace CalcEngine
 
     Rational::Rational(uint64_t ui)
     {
-        uint32_t hi = HIDWORD(ui);
-        uint32_t lo = LODWORD(ui);
+        uint32_t hi = (uint32_t) (((ui) >> 32) & 0xffffffff);
+        uint32_t lo = (uint32_t) ui;
 
         Rational temp = (Rational{ hi } << 32) | lo;