Split NASM preprocessor standard macro set between various modules.

Split NASM preprocessor standard macro set between various modules.
Standard macro sets are looked up based on parser and preprocessor keyword
from individual modules.

The "standard" NASM parser macros now reside in the NASM parser, so when
the GAS parser is used with the NASM preprocessor, the NASM-specific macros
are no longer defined.

Object-format specific macros are now individually defined by each object
formatm module.  This allows for the object formats to be independent of the
NASM preprocessor module and yields a small optimization benefit as unused
object format macros don't need to be skipped over.

Also add GAS macro equivalents for the Win64 SEH more complex directives [1].

[1] Requested by Brian Gladman <brg@gladman.plus.com>

svn path=/trunk/yasm/; revision=2082