More work on process spawning.

* Kernel now parses command lines, supporting backslash escaping and quote
  escaping.
* Generates argument strings.
* Untested implementation of an environment string parser.
* Userspace process swamps now begin at 0x100000 instead of 0x1000.
* Implemented strnlen[|8|16].
* New ERROR_* value, ERROR_LIMIT_OVERFLOWED.
* Process arguments now have a maxlength of 32,700 ucs-8 chars.
* Syscalls getProcessFullNameMaxLength(), getProcessArgumentsMaxLength().
* processTribC::SpawnStream(): now returns error_t and takes a pointer to
  a processStreamC for the second return value. Also has been slightly
  re-designed.
* Wrote a small script to grep the source for #ifdefs, as part of an effort to
  clean up the use of #ifdef in kernel source.