ARROW-3661: [Gandiva][GLib] Use "_" as word separator in constant name

[kou]

No description provided.

[kou]

@shiro615 Can you review this?

[codecov-io]

Codecov Report

Merging #2881 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2881      +/-   ##
==========================================
- Coverage   87.58%   87.57%   -0.02%     
==========================================
  Files         412      412              
  Lines       64036    64036              
==========================================
- Hits        56084    56077       -7     
- Misses       7882     7885       +3     
- Partials       70       74       +4

Impacted Files	Coverage Δ
go/arrow/math/int64_avx2_amd64.go	0% <0%> (-100%)	⬇️
go/arrow/memory/memory_avx2_amd64.go	0% <0%> (-100%)	⬇️
go/arrow/math/float64_avx2_amd64.go	0% <0%> (-100%)	⬇️
go/arrow/math/uint64_avx2_amd64.go	0% <0%> (-100%)	⬇️
go/arrow/memory/memory_amd64.go	28.57% <0%> (-14.29%)	⬇️
go/arrow/math/math_amd64.go	31.57% <0%> (-5.27%)	⬇️
go/arrow/math/float64_amd64.go	33.33% <0%> (ø)	⬆️
go/arrow/math/int64_amd64.go	33.33% <0%> (ø)	⬆️
go/arrow/math/uint64_amd64.go	33.33% <0%> (ø)	⬆️
cpp/src/arrow/csv/column-builder.cc	97.1% <0%> (+2.17%)	⬆️
... and 4 more

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[shiro615]

LGTM

[praveenbingo]

code review +1.

[xhochy]

+1, LGTM