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/custom-formatter-test.cc

@@ -22,13 +22,21 @@ class custom_arg_formatter :
   using base::operator();
 
   iterator operator()(double value) {
-    if (round(value * pow(10, spec().precision())) == 0)
+#if FMT_GCC_VERSION
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wfloat-equal"
+#endif
+    // Comparing a float to 0.0 is safe
+    if (round(value * pow(10, spec().precision())) == 0.0)
       value = 0;
     return base::operator()(value);
+#if FMT_GCC_VERSION
+#pragma GCC diagnostic pop
+#endif
   }
 };
 
-std::string custom_vformat(fmt::string_view format_str, fmt::format_args args) {
+static std::string custom_vformat(fmt::string_view format_str, fmt::format_args args) {
   fmt::memory_buffer buffer;
   // Pass custom argument formatter as a template arg to vwrite.
   fmt::vformat_to<custom_arg_formatter>(buffer, format_str, args);