Conditional breakpoints
=========================
conditional breakpoints are implemented in the following way:
- when a breakpoint is hit, the condition is run as a normal command
- if the command returns a value different from zero, execution continue,
- otherwise, execution is stopped at the breakpoint

 Examples of conditional breakpoints
======================================
1.) ignore breakpoint at address 0x4000ce for five times:
	f times=5
	(dec_times,f times=`?vi times-1,?= times)
	db 0x4000ce
	dbC 0x4000ce .(dec_times)
	dc
2.) execute until rax==0x31c0 at address 0x4000ce
	e cmd.hitinfo=0
	(break_rax,f reg_rax=`dr rax`,f test=`?vi reg_rax-0x31c0`,?= test)
	db 0x4000ce
	dbC 0x4000ce .(break_rax)
	dc
3.) perform a register tracing dump at address 0x4000ce
	e cmd.hitinfo=0
	(trace_rax,dr rax,?= 1)
	db 0x4000ce
	dbC 0x4000ce .(trace_rax)
	dc > trace.txt