disasm/asm: Support "<arch>.<syscall>"

[david942j]

disasm: support inferring the syscall name when there is only one possible architecture
asm: support considering <arch>.<syscall> as a valid syntax

A = arch
if (A != ARCH_X86_64) goto i386
A = sys_number
if (A >= 0x40000000) goto dead
if (A == 0) goto allow
if (A == 1) goto allow
if (A == 2) goto allow else goto dead

i386: if (A != ARCH_I386) goto arm64
A = sys_number
if (A == 0) goto allow
if (A == 1) goto allow
if (A == 2) goto allow else goto dead

arm64: if (A != ARCH_AARCH64) goto s390x
A = sys_number
if (A == 0) goto allow
if (A == 1) goto allow
if (A == 2) goto allow else goto dead

s390x: if (A != ARCH_S390X) goto dead
A = sys_number
if (A == 0) goto allow
if (A == 1) goto allow
if (A == 2) goto allow else goto dead

dead: return KILL
allow: return ALLOW

Will be disasm-ed as

 line  CODE  JT   JF      K
=================================
 0000: 0x20 0x00 0x00 0x00000004  A = arch
 0001: 0x15 0x00 0x05 0xc000003e  if (A != ARCH_X86_64) goto 0007
 0002: 0x20 0x00 0x00 0x00000000  A = sys_number
 0003: 0x35 0x12 0x00 0x40000000  if (A >= 0x40000000) goto 0022
 0004: 0x15 0x12 0x00 0x00000000  if (A == read) goto 0023
 0005: 0x15 0x11 0x00 0x00000001  if (A == write) goto 0023
 0006: 0x15 0x10 0x0f 0x00000002  if (A == open) goto 0023 else goto 0022
 0007: 0x15 0x00 0x04 0x40000003  if (A != ARCH_I386) goto 0012
 0008: 0x20 0x00 0x00 0x00000000  A = sys_number
 0009: 0x15 0x0d 0x00 0x00000000  if (A == i386.restart_syscall) goto 0023
 0010: 0x15 0x0c 0x00 0x00000001  if (A == i386.exit) goto 0023
 0011: 0x15 0x0b 0x0a 0x00000002  if (A == i386.fork) goto 0023 else goto 0022
 0012: 0x15 0x00 0x04 0xc00000b7  if (A != ARCH_AARCH64) goto 0017
 0013: 0x20 0x00 0x00 0x00000000  A = sys_number
 0014: 0x15 0x08 0x00 0x00000000  if (A == aarch64.io_setup) goto 0023
 0015: 0x15 0x07 0x00 0x00000001  if (A == aarch64.io_destroy) goto 0023
 0016: 0x15 0x06 0x05 0x00000002  if (A == aarch64.io_submit) goto 0023 else goto 0022
 0017: 0x15 0x00 0x04 0x80000016  if (A != ARCH_S390X) goto 0022
 0018: 0x20 0x00 0x00 0x00000000  A = sys_number
 0019: 0x15 0x03 0x00 0x00000000  if (A == 0x0) goto 0023
 0020: 0x15 0x02 0x00 0x00000001  if (A == s390x.exit) goto 0023
 0021: 0x15 0x01 0x00 0x00000002  if (A == s390x.fork) goto 0023
 0022: 0x06 0x00 0x00 0x00000000  return KILL
 0023: 0x06 0x00 0x00 0x7fff0000  return ALLOW

Fixes #204