When matching a caret, the expression `f->gototab[s][c] = f->curstat;` in
cgoto() will index the 2D-array gototab with [s][261]. However, gototab
is declared as being of size [NSTATES][NCHARS], so [32][259]. Therefore,
this assignment will write to the state for character 0x1.
I'm not sure how to create a regression test for this, but increasing the
array size to HAT+1 values fixes the error and the tests still pass.
I found this issue while running awk on a CHERI system with sub-object
protection enabled. On x86, this can be reproduced by compiling awk
with -fsanitize=undefined.
