Use `true` instead of `1` as default value for `is_compressed bool` field

[asfimport]

I noticed that the default value for the optional boolean is_compressed field of the DataPageHeaderV2 struct has a default value of 1. According to the Thrift docs a boolean value is either true or false. 

This currently works because the Apache Thrift compiler internally handles bools as ints:

• https://github.com/apache/thrift/blob/3880a09565a9a1dad028b3679746eafac268c819/compiler/cpp/src/thrift/thriftl.ll#L208-L209

• https://github.com/apache/thrift/blob/3880a09565a9a1dad028b3679746eafac268c819/compiler/cpp/src/thrift/main.cc#L748

  It may however not work with other Thrift compilers that are more strict about this.

  Based on the docs and a test (https://github.com/apache/thrift/blob/3880a09565a9a1dad028b3679746eafac268c819/test/ThriftTest.thrift#L406) in the Thrift repository it seems that using true here is the correct way of defining a default for an optional bool field.

   

Reporter: Matthijs Brobbel / @mbrobbel Assignee: Matthijs Brobbel / @mbrobbel

Externally tracked issue: https://github.com/apache/parquet-format/pull/210

_{Note: This issue was originally created as PARQUET-2299. Please see the migration documentation for further details.}