Add Support for Postgres 9.3

Build System: Add Support for Postgres 9.3 and cleanup of cmake build targets 

Jira: MADLIB-782 
1) Adds the new port folder for Postgres 9.3
2) Adjusts the cmake FindPostgres function to handle REGEX REPLACE better so that it outputs reasonable error messages.
3) Replaces all occurrences of int4 with int32 due to removal of the int4 alias in postgres 9.3
4) Adds #include for htup_details.h for functions that access HeapTuple or heap_form_tuple directly.
5) Adds #include for various system headers no longer included by the postgres headers.