Allow extra specialisation for ISSET/ISEMPTY handlers

Reduce overhead of extra-specialization for opcode handler selection.

Merge branch 'PHP-7.2'

* PHP-7.2:
Fixed user-opcode support

Fixed user-opcode support

Allow generation of VM map

Mark exceptional helpers as "cold"

fix ZEND_VM_SET_OPCODE_HANDLER cannot set user opcode handler

Fixed typo

Added VM instrumentation ability

Elimintate duplicate error message

Avoid live range references in opcodes

Don't store the live range of the freed variable for FREE_ON_RETURN
frees, instead look it up at runtime. As this is an extremely
unlikely code

Avoid live range references in opcodes

Don't store the live range of the freed variable for FREE_ON_RETURN
frees, instead look it up at runtime. As this is an extremely
unlikely codepath (in particular, it requires a loop variable with
a throwing destructor), saving the runtime lookup of the live range
is not worth the extra complexity this adds everywhere else.

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Optimize "backup" functions of inlined opcode handlers for size

Added ability to manually sort opcode handlers (not used yet)

Added simple VM instrumentation ability

Avoid inlining of rarely used handlers

fix unknown opcode overflow error

Moved "zval.u2.cache_slot" into free room of "zend_op"

Avoid repeatable ARG_SHOULD_BE_SENT_BY_REF() checks in FETCH_*FUNC_ARG and following SEND_VAR_EX. Perform the check once in a new CHECK_FUNC_ARG opcode and reuse in the following FETCH_*FUNC_ARG and

Avoid repeatable ARG_SHOULD_BE_SENT_BY_REF() checks in FETCH_*FUNC_ARG and following SEND_VAR_EX. Perform the check once in a new CHECK_FUNC_ARG opcode and reuse in the following FETCH_*FUNC_ARG and SEND_FUNC_ARG (SEND_VAR_EX replacement).

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Changed CATCH instruction format (extended_value moved into op2, op2 into result, result into extended_value)

Changed FETCH_CONSTANT instruction format (extended_value moved into op1)

Changed FETCH_CLASS instruction format (extended_value moved into op1)

Compress handlers table

Make IS_UNUSED to be zero.

Use fastcall calling convention

Added abiliy to mark object specific handlers with most often used operand types as HOT. (UNUSED+CONST and CV+CONST)