Refactoring of idl_parser (#4948)

* Refactoring of numbers parser

More accurate parse of float and double.
Hexadecimal floats.
Check "out-of-range" of uint64 fields.
Check correctness of default values and metadata.

* Remove locale-independent code strtod/strtof from PR #4948.

* small optimization

* Add is_(ascii) functions

* is_ascii cleanup

* Fix format conversation

* Refine number parser

* Make code compatible with Android build

* Remove unnecessary suppression of warning C4127

src/idl_gen_cpp.cpp

@@ -145,7 +145,7 @@ class CppGenerator : public BaseGenerator {
     std::string guard = file_name_;
     // Remove any non-alpha-numeric characters that may appear in a filename.
     struct IsAlnum {
-      bool operator()(char c) const { return !isalnum(c); }
+      bool operator()(char c) const { return !is_alnum(c); }
     };
     guard.erase(std::remove_if(guard.begin(), guard.end(), IsAlnum()),
                 guard.end());