Accomodate Enum init deprecation

[marler8997]

PR dlang/dmd#7996 is modifying the compiler to comply with the language specification:

The value of an EnumMember is given by its AssignExpression. If there is no AssignExpression and it is the first EnumMember, its value is EnumBaseType.init.

The current behavior is to assign the value 0 to the first enum member when no assign expression is given. The referenced PR introduces a deprecation message when an enum's base type's .init member is not 0. This applies to the types double, char and real. This allows applications to maintain the current behavior for a time until the deprecation is over and the behavior will change to match the specification. Note that this means you cannot currently create an enum with base type double, char or real without a deprecation message unless you give it's first member an explicit assignment. Since phobos treats deprecations as errors, this PR provides explicit assignments in these cases during this deprecation period.

[dlang-bot]

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Testing this PR locally

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[JackStouffer]

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