libobs/util: Remove old ifdefs

These defs inadvertently redefinine `std::strtoll` in C++ code
that includes the header, causing lots of problems. They only
serve to provide compatability with very old MSVC versions.
As such, they can just be removed entirely.

libobs/util/platform.h

@@ -197,13 +197,6 @@ EXPORT bool os_get_proc_memory_usage(os_proc_memory_usage_t *usage);
 EXPORT uint64_t os_get_proc_resident_size(void);
 EXPORT uint64_t os_get_proc_virtual_size(void);
 
-#ifdef _MSC_VER
-#define strtoll _strtoi64
-#if _MSC_VER < 1900
-#define snprintf _snprintf
-#endif
-#endif
-
 /* clang-format off */
 #ifdef __APPLE__
 # define ARCH_BITS 64