Removed IS_STR_OFFSET type and corresponding macros. Optimized string offset handling in ASSIGN_DIM opcode.
Fix parser stack destruction with dummy ENCAPSED_AND_WHITESPACE

T_ENCAPSED_AND_WHITESPACE is now specified to always hold a value,
so give it a NULL value in the dummy cases.
Added ability to make a number of "warmup" requests before an actual benchmark.
(php-cgi -T [<number-of-warmup-requests>,]<number-of-benchmark-requests> <file>)