Fix in standard function library: forgot static linkage for inline __str_cmp()

Fixed in standard function library: NE_BOOL was missing.

Fixed in standard function library: String comparison was retrurning wrong result whith strings of different sizes but starting the same, or with zero length strings.

Fixed FIND Standard Character String Function. Now returns 0 in case empty string is given either for IN1 or IN2.

Reworked get_greatest_tick_count computation

Add a column to VARIABLES.CSV, containing variable (derived) type name, additionally to current last column contyaining base type name

add default NULL value to references (as suggested by anonymous in issue 62)
(Not really needed, but it is good practise...)

merge

fix issue #73: add missing overloaded functions ADD, SUB, MUL and DIV for TIME, TOD, DT, ...

remove debugging printf() introduced in previous commits

merge

fix bug introduced in previous commit (force literals to unsigned log long)

return storage of task interval back to 1 ns resolution (when calculating least common multiple et. al. of task intervals).

addendum to issue #76: detect overflow when calculating least common multiple of task intervals.

definitive fix of issue #76: remove internal overflow of u64 when calculating least common multiple of task intervals.