libcgc: only write the first swizzle-agument for scalar-op

Signed-off-by: Erik Faye-Lund <kusmabite@gmail.com>
libcgc: Rename mnemonics

Let's use a bit more standard opcode-mnemonics. Make all
mnemonics 3 letters long.

Signed-off-by: Erik Faye-Lund <kusmabite@gmail.com>
libcgc: Write register indices in base10

Signed-off-by: Erik Faye-Lund <kusmabite@gmail.com>
libcgc: Only output third operand if possibly needed

Signed-off-by: Erik Faye-Lund <kusmabite@gmail.com>
libcgc: Write instruction in an ASM-like syntax

Signed-off-by: Erik Faye-Lund <kusmabite@gmail.com>