Externals: Add libfmt 5.3.0 to externals

Allows us to migrate off of printf specifiers and have more type-safe
formatting facilities. It also allows for custom type support as well.
fmt is also on track to have part of it standardized within C++2a, so
this will also lessen the transitional work necessary later on by
allowing new code to use it.

This simply adds the library but doesn't do anything with it yet.

Externals/fmt/support/cmake/FindSetEnv.cmake

@@ -0,0 +1,7 @@
+# A CMake script to find SetEnv.cmd.
+
+find_program(WINSDK_SETENV NAMES SetEnv.cmd
+  PATHS "[HKEY_LOCAL_MACHINE\\SOFTWARE\\Microsoft\\Microsoft SDKs\\Windows;CurrentInstallFolder]/bin")
+if (WINSDK_SETENV AND PRINT_PATH)
+  execute_process(COMMAND ${CMAKE_COMMAND} -E echo "${WINSDK_SETENV}")
+endif ()

Externals/fmt/support/cmake/cxx14.cmake

@@ -0,0 +1,97 @@
+# C++14 feature support detection
+
+include(CheckCXXSourceCompiles)
+include(CheckCXXCompilerFlag)
+
+if (NOT CMAKE_CXX_STANDARD)
+  set(CMAKE_CXX_STANDARD 11)
+endif()
+message(STATUS "CXX_STANDARD: ${CMAKE_CXX_STANDARD}")
+
+if (CMAKE_CXX_STANDARD EQUAL 20)
+  check_cxx_compiler_flag(-std=c++20 has_std_20_flag)
+  check_cxx_compiler_flag(-std=c++2a has_std_2a_flag)
+
+  if (has_std_20_flag)
+    set(CXX_STANDARD_FLAG -std=c++20)
+  elseif (has_std_2a_flag)
+    set(CXX_STANDARD_FLAG -std=c++2a)
+  endif ()
+elseif (CMAKE_CXX_STANDARD EQUAL 17)
+  check_cxx_compiler_flag(-std=c++17 has_std_17_flag)
+  check_cxx_compiler_flag(-std=c++1z has_std_1z_flag)
+
+  if (has_std_17_flag)
+    set(CXX_STANDARD_FLAG -std=c++17)
+  elseif (has_std_1z_flag)
+    set(CXX_STANDARD_FLAG -std=c++1z)
+  endif ()
+elseif (CMAKE_CXX_STANDARD EQUAL 14)
+  check_cxx_compiler_flag(-std=c++14 has_std_14_flag)
+  check_cxx_compiler_flag(-std=c++1y has_std_1y_flag)
+
+  if (has_std_14_flag)
+    set(CXX_STANDARD_FLAG -std=c++14)
+  elseif (has_std_1y_flag)
+    set(CXX_STANDARD_FLAG -std=c++1y)
+  endif ()
+elseif (CMAKE_CXX_STANDARD EQUAL 11)
+  check_cxx_compiler_flag(-std=c++11 has_std_11_flag)
+  check_cxx_compiler_flag(-std=c++0x has_std_0x_flag)
+
+  if (has_std_11_flag)
+    set(CXX_STANDARD_FLAG -std=c++11)
+  elseif (has_std_0x_flag)
+    set(CXX_STANDARD_FLAG -std=c++0x)
+  endif ()
+endif ()
+
+set(CMAKE_REQUIRED_FLAGS ${CXX_STANDARD_FLAG})
+
+# Check if variadic templates are working and not affected by GCC bug 39653:
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=39653
+check_cxx_source_compiles("
+  template <class T, class ...Types>
+  struct S { typedef typename S<Types...>::type type; };
+  int main() {}" SUPPORTS_VARIADIC_TEMPLATES)
+if (NOT SUPPORTS_VARIADIC_TEMPLATES)
+  set (SUPPORTS_VARIADIC_TEMPLATES OFF)
+endif ()
+
+# Check if initializer lists are supported.
+check_cxx_source_compiles("
+  #include <initializer_list>
+  int main() {}" SUPPORTS_INITIALIZER_LIST)
+if (NOT SUPPORTS_INITIALIZER_LIST)
+  set (SUPPORTS_INITIALIZER_LIST OFF)
+endif ()
+
+# Check if enum bases are available
+check_cxx_source_compiles("
+  enum C : char {A};
+  int main() {}"
+  SUPPORTS_ENUM_BASE)
+if (NOT SUPPORTS_ENUM_BASE)
+  set (SUPPORTS_ENUM_BASE OFF)
+endif ()
+
+# Check if type traits are available
+check_cxx_source_compiles("
+  #include <type_traits>
+  class C { void operator=(const C&); };
+  int main() { static_assert(!std::is_copy_assignable<C>::value, \"\"); }"
+  SUPPORTS_TYPE_TRAITS)
+if (NOT SUPPORTS_TYPE_TRAITS)
+  set (SUPPORTS_TYPE_TRAITS OFF)
+endif ()
+
+# Check if user-defined literals are available
+check_cxx_source_compiles("
+  void operator\"\" _udl(long double);
+  int main() {}"
+  SUPPORTS_USER_DEFINED_LITERALS)
+if (NOT SUPPORTS_USER_DEFINED_LITERALS)
+  set (SUPPORTS_USER_DEFINED_LITERALS OFF)
+endif ()
+
+set(CMAKE_REQUIRED_FLAGS )

Externals/fmt/support/cmake/fmt-config.cmake.in

@@ -0,0 +1,4 @@
+@PACKAGE_INIT@
+
+include(${CMAKE_CURRENT_LIST_DIR}/@targets_export_name@.cmake)
+check_required_components(fmt)

Externals/fmt/support/cmake/fmt.pc.in

@@ -0,0 +1,11 @@
+prefix=@CMAKE_INSTALL_PREFIX@
+exec_prefix=@CMAKE_INSTALL_PREFIX@
+libdir=@CMAKE_INSTALL_FULL_LIBDIR@
+includedir=@CMAKE_INSTALL_FULL_INCLUDEDIR@
+
+Name: fmt
+Description: A modern formatting library
+Version: @FMT_VERSION@
+Libs: -L${libdir} -lfmt
+Cflags: -I${includedir}
+

Externals/fmt/support/cmake/run-cmake.bat

@@ -0,0 +1,11 @@
+@echo on
+rem This scripts configures build environment and runs CMake.
+rem Use it instead of running CMake directly when building with
+rem the Microsoft SDK toolchain rather than Visual Studio.
+rem It is used in the same way as cmake, for example:
+rem
+rem   run-cmake -G "Visual Studio 10 Win64" .
+
+for /F "delims=" %%i IN ('cmake "-DPRINT_PATH=1" -P %~dp0/FindSetEnv.cmake') DO set setenv=%%i
+if NOT "%setenv%" == "" call "%setenv%"
+cmake %*