CDH-18416: Don't inline ReadWriteUtil::ReadZLong()

For wide Avro tables, ReadZLong() would get inlined many times into a
single function body, causing LLVM to crash. Not inlining doesn't seem
to have a performance impact on narrow tables, and helps with wide
tables.

This change also adds tests over wide (i.e. many-column) tables. The
test tables are produced by specifying shell commands to generate test
tables in functional_schema_template.sql, which are executed in
generate-schema-statements.py. In the SQL templates, sections starting
with a ` are treated as shell commands. The output of the shell
command is then used as the section text. This is only a starting
point; it isn't currently implemented for all sections, and may have
to be tweaked if we use this mechanism for all tables.

Change-Id: Ife0d857d19b21534167a34c8bc06bc70bef34910
Reviewed-on: http://gerrit.ent.cloudera.com:8080/2206
Reviewed-by: Skye Wanderman-Milne <skye@cloudera.com>
Tested-by: Skye Wanderman-Milne <skye@cloudera.com>