[breaking] Rewrite the C API using Clang.jl

[odow]

This PR rewrites much of ECOS.jl in order to use the automated wrapper of the
C API generated by Clang.jl.

Closes #116
Closes #117

[codecov]

Codecov Report

Merging #128 (d9a184b) into master (c650e45) will decrease coverage by 3.13%.
The diff coverage is 84.37%.

@@            Coverage Diff             @@
##           master     #128      +/-   ##
==========================================
- Coverage   79.25%   76.11%   -3.14%     
==========================================
  Files           4        3       -1     
  Lines         241      201      -40     
==========================================
- Hits          191      153      -38     
+ Misses         50       48       -2     

Impacted Files	Coverage Δ
src/MOI_wrapper/permuted_exponential_cone.jl	87.50% <ø> (ø)
src/MOI_wrapper/MOI_wrapper.jl	74.13% <83.33%> (ø)
src/ECOS.jl	90.90% <90.00%> (-6.53%)	⬇️

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