Reduce number of disasm*() methods

[tmfink]

Address comments from:
#115 (review)

[jiegec]

There is a small place where the existing disasm_all/disasm_count is more convenient: disasm_iter does not allow having two Insn at the same time (due to sharing their details pointer).

[jiegec]

There is a small place where the existing disasm_all/disasm_count is more convenient: disasm_iter does not allow having two Insn at the same time (due to sharing their details pointer).

Therefore, I prefer to keep the existing ones and suggest performance-sensitive users to switch over.