Eliminate duplicated allocations of at-cfunction for libsvm_set_verbose

[iblislin]

No description provided.

[codecov-commenter]

Codecov Report

Merging #78 (975948d) into master (76e57ad) will increase coverage by 0.45%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #78      +/-   ##
==========================================
+ Coverage   82.88%   83.33%   +0.45%     
==========================================
  Files           5        5              
  Lines         222      222              
==========================================
+ Hits          184      185       +1     
+ Misses         38       37       -1     

Impacted Files	Coverage Δ
src/LIBSVM.jl	92.07% <100.00%> (+0.60%)	⬆️
src/libcalls.jl	85.71% <100.00%> (ø)

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