Bugfix: allow compilation with __DEBUG__.

The argument idx_ is only used in an ASSERT; ASSERT, in turn, is a
no-op unless __DEBUG__ is defined.  So, when __DEBUG__ is not defined,
gcc would warn about an unused variable if the name is declared.

Allow debug and warning-free non-debug compilation to occur by making
argument name declaration conditional on __DEBUG__.
Bugfix: change isAccessedTransposed() to doAccessTransposed.

This is a best-guess fix to allow compilation when __DEBUG__ is defined.
Buildfix: Define __DEBUG__ for CMAKE_BUILD_TYPE Debug.

This seems like the likely intent of the conditional compilation
on__DEBUG__ in acado_debugging.hpp, etc.

It might be better to take a leaf out of <assert.h>, and use NDEBUG
instead.
WarningFix: remove always-true expression in assertion.

The variable being checked for non-negativity is an unsigned int.
Bugfix: acadoIsEqual should use fabs() for rel vs abs decision.

Code previously used maximum of signed arguments to decide whether to
use relative or absolute tolerance check.  If this function is to also
be used to compare negative numbers of large magnitude, the absolute
value of its arguments should be used.
Minor: whitespace fix.
Merge branch 'debug-fixes' of github.com:roryyorke/acado into roryyorke-debug-fixes
Merge branch 'isequal-uses-fabs-2' of github.com:roryyorke/acado into roryyorke-isequal-uses-fabs-2
Removed some warnings