Improve FGdbDatasource to use API Geodatabase::ExecuteSQL

[jpalmer]

It would be really good to change the current implementation of FGdbDatasource::ExecuteSQL to pass calls to the FileGDB API Geodatabase::ExecuteSQL() by default. This would then take advantage of the Esri FileGDB SQL engine.

Apart from the obvious speed enhancements you would gain by using this method, users would also get the ability to create table indices. e.g

ogrinfo -sql 'CREATE INDEX my_table_id_idx ON my_table (id)' myfile.gdb

[Even Rouault]

trunk r25025 "FileGDB: use File GDB SDK API for SQL statements. Note that due to to partial/inaccurate support for SELECT statements in current FileGDB SDK API versions (v1.2), SELECT statements will be run by default by the OGR SQL engine, unless the FileGDB dialect is explicitely specified (#4839)"

[jpalmer]

Wow Even! Works fantastic. Thank you very much.