asm: Add asm_emit_* macros

These are just lower-case aliases for the AsmEmit* functions.
asm: Add AsmInitPtr()
amx_header: Minor cleanup
asm: Add asm_emit_jcc_rel macros for Rel version of EmitJcc
asm: Fix opcode and function name

The correct name is push.adr, not push.addr, and the opcode constant
is actually called OP_PUSH_ADR, with a single D, so the function would
not compile anyway.
asm: Fix missing tag
asm: Add AsmEmitBreak()
Merge https://github.com/Zeex/amx_assembly

Conflicts:
	asm.inc