Uninit variable in uotool

In the function z_histogram(), zcount was not initialized and would produce wrong results for the histogram. Did anyone ever test this?
Fixed small bugs

statics_histogram() could have an out-of-bounds write if the count in a static block was larger than 1000.

readtile() and readlandtile() were not ensuring that the strings were null-terminated, which could cause a problem if a bad/corrupted file were read.