[Utility] Add std::string_view overloads for std::from_chars (#2392)

* Add std::string_view overloads for std::from_chars

std::from_chars floating point support is still pour, so we provide some
fall backs. These fall backs currently lack error handling.

(since GCC 11 and MSVC 2019 16.4 FP support is added, clang with libc++
still doesn't support FP)

GCC's floating point support is still rather pour (performance) and
probably shouldn't be used, but we have support to if people want to
now.

Probably need more test cases ...

* Fix issue with std::chars_format define lacking

My test case for lacking FP support was clang with libc++ which defined
this enum anyways.

common/strings.cpp

@@ -1,3 +1,4 @@
+// for folly stuff
 /*
  * Copyright 2013 Facebook, Inc.
  *
@@ -13,6 +14,24 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+// for our stuff
+/*	EQEMu: Everquest Server Emulator
+	Copyright (C) 2001-2022 EQEMu Development Team (http://eqemulator.net)
+
+	This program is free software; you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation; version 2 of the License.
+
+	This program is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY except by those people which sell it, which
+	are required to give you total support for your newly bought product;
+	without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+	A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with this program; if not, write to the Free Software
+	Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+*/
 
 #include "strings.h"
 #include <fmt/format.h>