Context-based output infrastructure (V3_Print, etc) and modifications to use it

Context-based output infrastructure (V3_Print, etc) and modifications to use it

This commit is huge, but the vast majority of it is basically trivial changes in
how V3_Print, PrintDebug, PrintError, V3_ASSERT, and Vnet_Print are invoked
throughout our codebase. All compiles, with all debug and features enabled.
Functionality testing doesn't show problems.

These functions now include a context: the VM and the vcore.  There are
Several cases:

V3_Print(vm, vcore, ...)           => VM-specific, and vcore-specific
V3_Print(vm, VCORE_NONE,...)       => VM-specific, but not core specific
V3_Print(VM_NONE, VCORE_NONE),...) => non-specific

PrintDebug now prefaces data with DEBUG:
PrintError now prefaces data with ERROR:
Telementry prefaces with telem.# (as before)

The print OS hook has been modified so that it is called with:

print(void *host_priv_data_from_create, // NULL = non-specific
      int vcore_number,                 // -1 = non-specific
      ...)

The linux implementation now uses this functionality to decorate its
output in an enhanced way:

palacios (pcore num): ...
palacios (pcore num vm name): ...
palacios (pcore num vm name vcore num):...

The new userspace tool v3_info filters and formats dmesg or /proc/kmsg
output in numerous ways so that you can, for example, focus on the
debugging output of a specfic core on a specific VM. Run without
arguments for help.

Other minor compilation fixes for ancient code.