also:
re-integrated stack_defs.nim back into stack.nim
why:
the v2 prefix of the file name was used as a visual aid when
comparing vm2 against vm sources
why:
vm2 enabled by ENABLE_VM2=1 behaves as vm without ENABLE_EVMC=1 until
it doesn't in some future fatch set. this leaves some wiggle room
to work on a vm copy without degrading the original implementation.
details:
+ additional make flag ENABLE_VM2=1 (or ENABLE_VM2=0 to explicitely disable)
+ when both flags ENABLE_EVMC=1 and ENABLE_VM2=1 are present, the former
flag ENABLE_EVMC=1 takes precedence, this is implemented at the NIM
compiler level for -d:evmc_enabled and -d:vm2_enabled
Jordan Hrycaj