BUG: compiler allows 0 to be specified as a slice index

[legezam]

Although slicing syntax uses 1 based indexing for use convenience, it allows the user to specify 0 as an index, so foo2 and foo5 below compiles without any issues:

#refgenome cenpk
#warnoff zeronine
#linkers D0,D5,D6,D9|
#platform stitch
#name foo1
gHO[1:100] // ATG...
#name foo2
gHO[0:100] // ATG..  == foo1
#name foo3
gHO[-1:100] // A ATG...
#name foo4
gHO[1AE:5AE] // AAT...
#name foo5
gHO[0AE:5AE] // AAT... == foo4
#name foo6
gHO[-1AE:5AE] // TAA ATG...

Not a big deal but it should disallow this and raise a compilation error such as: Slice index cannot be zero