Rework roparg filler

Changes how the roparg filler is used slightly to allow filling with symbolic values.

See merge request !19

small rework of the roparg_filler to allow filling with a symbolic value. This is particularly useful for automatic exploitation where the constraint solve should be used to pick the values of the chain fillers

created common.py to collect functions which are needed in multiple places.

It was not used in rop.py

If we dont want zeros in the ropchain:
rop.set_roparg_filler(0xdeadbeef)

chain += p32(0x8075932)	# mov eax, ebx; pop ebx; mov edx, esi; pop esi; pop ebp; ret
chain += p32(0x68732f6e)
chain += p32(0x112232fc)
chain += p32(0xdeadbeef)

If the string given to write_to_memory is not a multiple of 4 (or 8?), it will need to be padded by a fill byte. The fill byte was set to 0xff. This commit makes it possible to give the fill byte as an argument.

E.g. useful if we want to write bash strings, and fill it with spaces or hashtags.

If the user does not want that the shellcode contains certain bytes (e.g. newlines, 0x0 etc), he can now define it in the rop object with the set_badbytes function.

rop.load_gadgets("gadgets")
rop.set_badbytes([0x01, 0xf9, 0x93, 0x95, 0x96, 0x40])
chain = rop.write_to_mem(0x11223344, "abcdefgh")

functions which filter badbytes:
write_to_mem
add_to_mem
write_to_mem_v2
func_call
_get_single_ret
_find_reg_setting_gadgets
_filter_reg_setting_gadgets
_get_sufficient_partial_controllers

update for moved cgc stack



See merge request !18

Wip/boolector



See merge request !16

shrink stack to 80 dwords



See merge request !17

check syscall



See merge request !15

Fix/cfgfast fix



See merge request !14

Enable tests for patcherex



See merge request !13