If two tables have multiple joins and one of them was compatible then
the incompatible join detection would fail.
This patch moves the incompatible join detection so that every join is
checked. It also removes the incompatible join detection from
expressionstep as this is redundant and was causing some valid quries to
fail.
For the initial BLOB/TEXT pull request we put them in the same bucket as
VARBINARY, forcing many functions to be disabled. This patch enables the
same TEXT function support as VARCHAR.
* TEXT and BLOB now have separate identifiers internally
* TEXT columns are identified as such in system catalog
* cpimport only requires hex input for BLOB, not TEXT