Added --with-postgres[=DIR]

[doubaokun]

No description provided.

[codecov]

Codecov Report

Merging #57 (d3749a9) into master (1b19b4d) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #57   +/-   ##
=======================================
  Coverage   50.88%   50.88%           
=======================================
  Files          72       72           
  Lines       14542    14542           
=======================================
+ Hits         7399     7400    +1     
+ Misses       7143     7142    -1     

Impacted Files	Coverage Δ
src/os/async_thread.cc	69.73% <0.00%> (-0.44%)	⬇️
src/server/port.cc	50.27% <0.00%> (+0.27%)	⬆️
src/core/channel.cc	71.84% <0.00%> (+0.97%)	⬆️

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