(YYSTACK_REALLOC): Remove.

(YYSTACK_REALLOC): Remove.
(YYSTACK_ALLOC): Resurrect this macro, with its old meaning.
(YYSTACK_FREE, YYSTACK_GAP_MAX, YYSTACK_BYTES, YYSTACK_RELOCATE):
New macros.
(union yyalloc): New type.
(__yy_memcpy): Last arg is size_t, not unsigned int, to remove
an arbitrary restriction on hosts where size_t is wider than int.

(yyparse): Don't dump core if alloca or malloc fails; instead, report
a parser stack overflow.  Allocate just one block of memory for all
three stacks, instead of allocating three blocks; this typically is
faster and reduces fragmentation.

Do not limit the number of items in the stack to a value that fits
in 'int', as this is an arbitrary limit on hosts with 64-bit
size_t and 32-bit int.