Added test file for interval interpolation

The new implementation of track effects will allow interpolation between tremolo
and vibrato effect values.

Additionally, it is required to use 3 elements in the array used to set effect
values. The 3rd element then sets the number of ticks to slide to the new effect
values.

For this, a new argument will be added to BKTrackSetPtr and
BKTrackGetPtr to define the length of the given pointer. Which may also prevent
buffer overflows.
Added better comments
Added slide state

This struct is used to interpolate between two values in a specific number of
steps. The interpolated value can rounded to be more accurate when using small
values.
Rewritten the most of the code

Added comments and better implementation for interpolating interval values.
Next the file will be splitted into a header and implementation file.
Removed round option

The returned value is now always rounded to the nearest value which creates
better values.
Splitted file BKIntervalState.c into BKInterpolation.h and BKInterpolation.c

Also moved test code into BKInterpolationTest.c
Moved constants into header file

Constant name appears in function description but was not visible in header.
Added description for `maxValue`

Copied description for `maxValue` from other comment.
Fixed variable alignment

Struct field was renamed to a shorter name.
Renamed and added functions to interpolation state

The added functions allow to change only single values of the states instead of
having to change them together.
Rewritten the track implementation to use the new interpolation states

Parts which affect the effect handling are rewritten to use the new
interpolation states. This is much cleaner and allows also to implement sliding
between tremolo and vibrato values which will be done next.
Setting update flags when updating attributes

Instead of updating the underlaying unit directly when changing track attributes
update flags are set. This can reduce duplicate function calls to the unit.

The unit is now updated in BKTrackTick and the new added BKTrackRun function.
BKTrackRun function does now update the unit before calling BKUnitRun.
Fixed some compiler warnings

Removed a manual warning which is now implemented in the track. Initialized var
to ensure that it is not uninitialized.
Set version to v0.3.2

Update makefiles to new version and add new example and template file for
bliplay.
Merge branch 'v0.3.2' into develop

Conflicts:
	configure
	configure.ac
Move test program into test directory

This program was used in branch v0.3.2 to test the new interpolation functions.
Update autotool version

After merging there was a version missmatch which should be corrected now.