Fix wrong printf types for timestamps
      
Use the correct printf macro to print uint64_t types.

This also fixes this warning:
  warning: format ‘%llu’ expects argument of type ‘long long unsigned int’, but
  argument 2 has type ‘uint64_t {aka long unsigned int}’ [-Wformat=]
Fix warnings for ignored pcs attributes

Only declare the calling convention for IMPLEMENT_SF_FUNCTION1 on arm, as the
pcs attribute is not valid on any other platform and generates lots of
warnings:

  warning: ‘pcs’ attribute directive ignored [-Wattributes]
Fix all compiler warnings.

Approved by Ricardo Mendoza, PS Jenkins bot.