ARROW-3641: [Python] Remove unneeded public keyword from pyarrow public C APIs
ARROW-3641: [Python] Remove unneeded public keyword from pyarrow public C APIs

According to

https://cython.readthedocs.io/en/latest/src/userguide/external_C_code.html#c-api-declarations

it is not necessary to use `public` here. If we want to be able to refer to Cython extension types at the C API level (at some point, this may not be a bad idea), then we must use `public` with those.

Author: Wes McKinney <wesm+git@apache.org>

Closes #3147 from wesm/ARROW-3641 and squashes the following commits:

f09902cb4 <Wes McKinney> Remove unneeded public keyword from pyarrow public APIs

apache/arrow,pcmoritz/arrow,apache/arrow,apache/arrow,majetideepak/arrow,cpcloud/arrow,tebeka/arrow,cpcloud/arrow,pcmoritz/arrow,itaiin/arrow,majetideepak/arrow,renesugar/arrow,renesugar/arrow,kou/arrow,xhochy/arrow,xhochy/arrow,laurentgo/arrow,xhochy/arrow,majetideepak/arrow,cpcloud/arrow,wesm/arrow,pcmoritz/arrow,itaiin/arrow,apache/arrow,xhochy/arrow,laurentgo/arrow,wesm/arrow,xhochy/arrow,wesm/arrow,laurentgo/arrow,wesm/arrow,icexelloss/arrow,cpcloud/arrow,renesugar/arrow,laurentgo/arrow,apache/arrow,pcmoritz/arrow,kou/arrow,kou/arrow,pcmoritz/arrow,icexelloss/arrow,majetideepak/arrow,icexelloss/arrow,cpcloud/arrow,renesugar/arrow,xhochy/arrow,xhochy/arrow,kou/arrow,cpcloud/arrow,cpcloud/arrow,icexelloss/arrow,tebeka/arrow,xhochy/arrow,apache/arrow,laurentgo/arrow,icexelloss/arrow,pcmoritz/arrow,icexelloss/arrow,wesm/arrow,kou/arrow,wesm/arrow,cpcloud/arrow,kou/arrow,wesm/arrow,majetideepak/arrow,kou/arrow,kou/arrow,laurentgo/arrow,itaiin/arrow,itaiin/arrow,itaiin/arrow,majetideepak/arrow,wesm/arrow,renesugar/arrow,cpcloud/arrow,kou/arrow,cpcloud/arrow,wesm/arrow,icexelloss/arrow,icexelloss/arrow,kou/arrow,itaiin/arrow,cpcloud/arrow,tebeka/arrow,renesugar/arrow,wesm/arrow,icexelloss/arrow,pcmoritz/arrow,tebeka/arrow,xhochy/arrow,tebeka/arrow,apache/arrow,xhochy/arrow,kou/arrow,itaiin/arrow,laurentgo/arrow,apache/arrow,laurentgo/arrow,itaiin/arrow,kou/arrow,itaiin/arrow,laurentgo/arrow,laurentgo/arrow,apache/arrow,kou/arrow,tebeka/arrow,cpcloud/arrow,laurentgo/arrow,apache/arrow,itaiin/arrow,apache/arrow,pcmoritz/arrow,majetideepak/arrow,laurentgo/arrow,apache/arrow,icexelloss/arrow,xhochy/arrow,renesugar/arrow,renesugar/arrow,majetideepak/arrow,renesugar/arrow,tebeka/arrow,xhochy/arrow,wesm/arrow,renesugar/arrow,icexelloss/arrow,wesm/arrow,itaiin/arrow,cpcloud/arrow,itaiin/arrow,renesugar/arrow,xhochy/arrow,pcmoritz/arrow,laurentgo/arrow,majetideepak/arrow,majetideepak/arrow,apache/arrow,wesm/arrow,pcmoritz/arrow,icexelloss/arrow,renesugar/arrow,tebeka/arrow,majetideepak/arrow,pcmoritz/arrow,tebeka/arrow,itaiin/arrow,cpcloud/arrow,majetideepak/arrow,majetideepak/arrow,apache/arrow,renesugar/arrow,xhochy/arrow,tebeka/arrow,renesugar/arrow,majetideepak/arrow,pcmoritz/arrow,wesm/arrow,icexelloss/arrow,kou/arrow,itaiin/arrow,majetideepak/arrow,xhochy/arrow,itaiin/arrow,pcmoritz/arrow,icexelloss/arrow,pcmoritz/arrow,laurentgo/arrow,laurentgo/arrow,pcmoritz/arrow,renesugar/arrow