Allow VariableReference as NamedArgument value #66

Job	Run time
lint	14s
compatibility (./fluent.syntax)	14s
compatibility (fluent.syntax==0.17.0 six)	12s
compatibility (fluent.syntax==0.18.1 six)	11s
compatibility (fluent.syntax==0.19.0)	10s
test (ubuntu-latest, 3.12)	12s
test (windows-latest, 3.13)	38s
test (windows-latest, 3.12)	44s
test (ubuntu-latest, 3.13)	12s
test (windows-latest, 3.10)	26s
test (ubuntu-latest, 3.10)	10s
test (ubuntu-latest, 3.9)	12s
test (ubuntu-latest, 3.14)	13s
test (ubuntu-latest, 3.11)	10s
test (windows-latest, 3.9)	29s
test (macos-latest, 3.14)	14s
test (macos-latest, 3.13)	14s
test (windows-latest, 3.11)	26s
test (windows-latest, 3.14)	28s
test (macos-latest, 3.10)	16s
test (macos-latest, 3.9)	13s
test (macos-latest, 3.11)	13s
test (macos-latest, 3.12)	14s
	6m 45s

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