Fix compilation with PORTABLE symbol.
Fix compilation with PORTABLE symbol.

Compiling with the PORTABLE symbol results in several errors.

> The namespace 'TinyIoC' already contains a definition for
> 'ReverseTypeExtender'

The NETSTANDARD1_6 symbol is OR'd instead of AND'd. Since the rest of
the symbols are AND'd, this appears to be a copy-and-paste error.

> Inconsistent accessibility: parameter type 'BindingFlags' is less
> accessible than method 'TypeExtensions.GetConstructors(Type,
> BindingFlags)'

The BindingFlags enum is marked internal; however, it is included in
various public method signatures.

grumpydev/TinyIoC