Remove some dead code.

CMakeLists.txt

@@ -7,8 +7,6 @@ set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH}
 set(CMAKE_CXX_STANDARD 11)
 set(CMAKE_CXX_STANDARD_REQUIRED YES)
 
-include(CheckIncludeFile)
-
 # for /MT on MSVC
 set(CMAKE_USER_MAKE_RULES_OVERRIDE
    "${CMAKE_SOURCE_DIR}/cmake/c_flag_overrides.cmake")

src/platform/unixutil.cpp

@@ -37,13 +37,6 @@ void ssremove(const std::string &filename)
     remove(filename.c_str());
 }
 
-int64_t GetUnixTime(void)
-{
-    time_t ret;
-    time(&ret);
-    return (int64_t)ret;
-}
-
 //-----------------------------------------------------------------------------
 // A separate heap, on which we allocate expressions. Maybe a bit faster,
 // since fragmentation is less of a concern, and it also makes it possible

src/platform/w32main.cpp

@@ -781,18 +781,6 @@ int64_t SolveSpace::GetMilliseconds(void)
     return (int64_t)d;
 }
 
-int64_t SolveSpace::GetUnixTime(void)
-{
-#ifdef __MINGW32__
-    time_t ret;
-    time(&ret);
-#else
-    __time64_t ret;
-    _time64(&ret);
-#endif
-    return (int64_t)ret;
-}
-
 void SolveSpace::InvalidateText(void)
 {
     InvalidateRect(TextWnd, NULL, false);

src/solvespace.h

@@ -245,7 +245,6 @@ bool FullScreenIsActive(void);
 void GetGraphicsWindowSize(int *w, int *h);
 void GetTextWindowSize(int *w, int *h);
 int64_t GetMilliseconds(void);
-int64_t GetUnixTime(void);
 
 void dbp(const char *str, ...);
 #define DBPTRI(tri) \