Conditional instructions, b2bf!

Now that's a large change!
This update features the following:

• Now, asm2bf has an internal flag register (inaccessible via normal means),
• The flag register can be set by the following: ceq cne cle clt cge cgt (equivalent to eq, ne, le, lt, ge, gt). For instance:

mov r1, 23
ceq r1, 23
; will set the flag register to 1.
ceq r1, 0
; nope, didn't succeed, now clears the flag register.

• New jumps: cjn cjz, that depend on the state of the flag register. For example:

; Old way (trashes r3):
mov r3, r1
eq_ r3, 10
jnz r3, %target

; New way (no trashes):
ceq r1, 10
cjn %target

• New instructions! All of these execute, whenever the flag register is set to 1:

Conditional variant: cad csu cmu cdi cmd csl csr cpw cps cpo csw crv cmo crc cst
Classic variant:     add sub mul div mod asl asr pow psh pop swp srv mov rcl sto

• b2bf (coined by comrade Maviek) - a B to asm2bf compiler. It's an initial release, so a few things in b2bf may be rigged, but it's able to produce decent code (just three times bigger than the handcoded and optimized assembly equivalent).