Remove unused variables.
Rewrite the assembly pipeline.

This patch uses SmxBuilder from spcomp2 to replace the old assemble()
pipeline. Instead of generating into an old AMX structure, and then
decoding that into SMX, we now directly generate into SMX. This greatly
simplifies code generation and smx building.
Add debug info tables to smxbuilder.
Re-add .dbg.natives.
Bump SourcePawn version to 1.7 to match SourceMod.
Use the correct string table for tag names.
Merge branch 'master' into calli-5

Conflicts:
	public/amtl/am-utility.h
Merge pull request #141 from alliedmodders/calli-5

Rewrite the assembly pipeline.