Fix #118: Don't use getcwd(NULL, 0), as it's platform-specific behavior.

Fix #118: Don't use getcwd(NULL, 0), as it's platform-specific behavior.

Instead write our own yasm__getcwd() which retries getcwd() with
increasing buffer sizes until the path fits (as the initial size is 1024,
in basically all cases it'll succeed on the first try).

Reported by: bird-yasm@anduin.net

svn path=/trunk/yasm/; revision=2004