Disassembler: Add support to cross-ref namespace twice if needed.

If a table must be parsed a second time due to the discovery
of external methods, now cross-ref the namespace again also.
This enables additional namespace support such as handling
notify disassembly comments on a per-object-type basis.
Disassembler: Miscellaneous updates for extern() handling.

1) Abort compiler if file specified by -fe option does not exist.
2) Silence unnecessary warnings about argument count mismatches.
3) Update warning messages concerning unresolved method externals.
iASL: Prevent possible infinite loop with -e option.

-e<file> with no space could loop forever.