Use the boolean_type_node setup by the middle-end instead of
redefining it. boolean_type_node is not used in GFortran for any
ABI-visible stuff, only internally as the type of boolean
expressions. There appears to be one exception to this, namely the
caf_get* and caf_send* calls which have boolean_type_node
arguments. However, on the library side they seem to use C _Bool, so I
suspect this might be a case of a argument mismatch that hasn't
affected anything so far.

The practical effect of this is that the size of such variables will
be the same as a C _Bool or C++ bool, that is, on most targets a
single byte. Previously we redefined boolean_type_node to be a Fortran
default logical kind sized variable, that is 4 or 8 bytes depending on
compile options. This might enable slightly more compact code, in case
the optimizer determines that the result of such a generated
comparison expression needs to be stored in some temporary location
rather than being used immediately.

Regression tested on x86_64-pc-linux-gnu.

2016-12-20  Janne Blomqvist  <jb@gcc.gnu.org>

	* trans-types.c (gfc_init_types): Don't redefine boolean type node.

From-SVN: r243830