Add more compilers to CI and increase FMT_PEDANTIC warning levels (#736)

* Add a _lot_ more warnings to FMT_PEDANTIC
Fix these warnings

* Add more compilers to CI
Fix (some) of the compiler errors with them

* Enable -Werror on CI
Increase warning level on MSVC when compiling with FMT_PEDANTIC

* Add VS 2013 and 2015 to Appveyor

* Fix Appveyor tests
Formatting

* Implement requested changes
Fix some of the MSVC warnings
Implement C++11 integer_sequence

* Reintroduce appveyor-build.py

* Remove ranges-test from tests

* Remove (some) explicit warning suppressions
Fix C++ standard setting in CI

* Remove (some) explicit warning suppressions
Fix C++ standard setting in CI

* Fix test builds with C++11

* Enable pedantic warnings on tests

* Fix warnings from edits to master

* Cleanups

* Add C++11 support to ranges.h
Re-enable ranges-test
Fix a Visual Studio error about function not returning a value in printf.h
Fix a bug in .travis.yml

test/time-test.cc

@@ -9,7 +9,7 @@
 #define _CRT_SECURE_NO_WARNINGS
 #endif
 
-#include "gmock/gmock.h"
+#include "gmock.h"
 #include "fmt/time.h"
 
 TEST(TimeTest, Format) {
@@ -26,7 +26,7 @@ TEST(TimeTest, GrowBuffer) {
   for (int i = 0; i < 30; ++i)
     s += "%c";
   s += "}\n";
-  std::time_t t = std::time(0);
+  std::time_t t = std::time(nullptr);
   fmt::format(s, *std::localtime(&t));
 }
 
@@ -34,7 +34,7 @@ TEST(TimeTest, EmptyResult) {
   EXPECT_EQ("", fmt::format("{}", std::tm()));
 }
 
-bool EqualTime(const std::tm &lhs, const std::tm &rhs) {
+static bool EqualTime(const std::tm &lhs, const std::tm &rhs) {
   return lhs.tm_sec == rhs.tm_sec &&
          lhs.tm_min == rhs.tm_min &&
          lhs.tm_hour == rhs.tm_hour &&
@@ -47,13 +47,13 @@ bool EqualTime(const std::tm &lhs, const std::tm &rhs) {
 }
 
 TEST(TimeTest, LocalTime) {
-  std::time_t t = std::time(0);
+  std::time_t t = std::time(nullptr);
   std::tm tm = *std::localtime(&t);
   EXPECT_TRUE(EqualTime(tm, fmt::localtime(t)));
 }
 
 TEST(TimeTest, GMTime) {
-  std::time_t t = std::time(0);
+  std::time_t t = std::time(nullptr);
   std::tm tm = *std::gmtime(&t);
   EXPECT_TRUE(EqualTime(tm, fmt::gmtime(t)));
 }