Generate an empty enum that compiles in C and Rust [patch]

[matt-edmondson]

Fixes #190

What changed

• C: CGenerator.GenerateEnumDeclaration always wrote typedef enum Name { … } Name;. ISO C does not allow an empty enumerator list, so gcc rejected the output for an enum with no members (empty enum is invalid). An enum with no members now becomes a typedef of its underlying type, or of int if none is set. A note explains that C has no empty enum, using the same WriteInexpressible style as the generator's other notes.
• Rust: rustc rejects #[repr] on an enum with no variants (E0084). RustGenerator.GenerateEnumDeclaration now omits it when Members is empty.

The other five targets already handled an empty enum, so they are unchanged.

Tests

• CGeneratorTests.Enum_WithNoMembers_IsATypedefOfItsType: Empty becomes typedef int Empty;, and Flags : long becomes typedef long long Flags;.
• CGeneratedSourceCompilesTests: the exemplar header now includes both empty enums and is compiled with -std=c11.
• RustGeneratorTests.Enum_WithNoVariants_HasNoRepr: checks that #[repr] is gone from an empty enum.
• RustGeneratedSourceCompilesTests: the exemplar now includes an empty enum with UnderlyingType = int and is compiled with rustc.

With the generator changes reverted, all four tests fail. gcc reports empty enum is invalid and rustc reports E0084. With the changes, the full suite passes (1102/1102).

This is separate from #181, the empty-struct case in C. That case goes through a different code path and is not touched here.

🤖 Generated with Claude Code

https://claude.ai/code/session_01X8BPy6trRZiUxiwJcbUGzR

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Generated by Claude Code

[sonarqubecloud]

Quality Gate passed

Issues
3 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

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