Use __restrict with gcc on the pike_interpreter

This produces the same code as const, but avoids lying to the compiler.

Fixed an issue with gcc 3.4, which over-optimized a bit (specifically,
pip->stack_pointer was not re-read between function calls, which seems
odd given that it is not pip->stack_pointer that was const...)
Fixed a few autodoc syntax errors.
Include file name and line in errors.
Count _decode and _encode as lfuns.
These functions are not really varargs.
Separate out operators from the normal methods in the refdoc.
Some minor documentation tweaks.

It has been a while since the classes were called Gz_deflate and Gz_inflate.
[autodoc] Added some minimal information about the Arg module
[autodoc] Added some minimal documentation to the Cache module
Added cast to Identifier
Use cast instead of _encode.
[autodoc] Added Calendar documentation from the FAQ.

It is actually rather useful. But very hard to find
[autodoc] Fixed erronous commit
[autodoc] Minimal pointers in Image module toplevel doc
Added note about the Shuffler to Pipe.Pipe.
Consistent formatting of function name parameter to get_all_args
[autodoc] Some reformatting.
[autodoc] Added note about extract_locale to the Locale module.
[autodoc] Removed import autodoc comment in Pango.

It was the only documented thing in the module
[autodoc] Document PDF.PDFgen create method