vtable and vtable size depends only on `Table#bb_pos` but calculated in
`Table#_offset` method on each field lookup.
Doing this with every call of `Table#__offset` is redundant.
These values can be read once with change of `Table#bb_pos` and reused
for any field lookup.
As recommended by https://golang.org/pkg/cmd/go/internal/generate/:
To convey to humans and machine tools that code is generated,
generated source should have a line early in the file that
matches the following regular expression (in Go syntax):
^// Code generated .* DO NOT EDIT\.$
* Added <autogenerated> in cs generator file header comment
#4287
* CS: Added xml-correct file header comment including "<auto-generated>...</auto-generated>"
code_generators.cpp: FlatBuffersGeneratedWarning() function replaced by compile time constant "GeneratedWarning"
also removed extra newlines at end of GeneratedWarning to be able to generate a xml well formed file comment for cs files
#4291
* code_generators: Changed static string GeneratedWarning back to function FlatBuffersGeneratedWarning()
#4291
* Added modified Unit-Test files
#4291
* idl_gen_general: Add autogenerated only in C# code
#4291
* C#: Fixed possible conflicts between usings and user-supplied namespace
C#: Added the global qualifier to using directives to prevent possible conflicts with the user-supplied namespace. Also prevents unintentional type hiding. Resolves issue #4242.
* Updated C# generated code files
