Also correct therefor to therefore.

Since both forms are arguably legal I wasn't sure about changing
this. But then Tom argued for 'therefore'...

Author: Dmitriy Olshevskiy
Discussion: 34789.1430067832@sss.pgh.pa.us

src/backend/libpq/pqcomm.c

@@ -1561,7 +1561,7 @@ socket_endcopyout(bool errorAbort)
 /*
  * On Windows, we need to set both idle and interval at the same time.
  * We also cannot reset them to the default (setting to zero will
- * actually set them to zero, not default), therefor we fallback to
+ * actually set them to zero, not default), therefore we fallback to
  * the out-of-the-box default instead.
  */
 #if defined(WIN32) && defined(SIO_KEEPALIVE_VALS)

src/backend/optimizer/geqo/geqo_erx.c

@@ -138,7 +138,7 @@ gimme_edge_table(PlannerInfo *root, Gene *tour1, Gene *tour2,
  *	  registers edge from city1 to city2 in input edge table
  *
  *	  no assumptions about directionality are made;
- *	  therefor it is up to the calling routine to
+ *	  therefore it is up to the calling routine to
  *	  call gimme_edge twice to make a bi-directional edge
  *	  between city1 and city2;
  *	  uni-directional edges are possible as well (just call gimme_edge