Changed Makefile to use bash from homebrew on Mac OS X

Homebrew (http://mxcl.github.io/homebrew/) is an alternative to
MacPorts, it installs all binaries in /usr/local/bin
Added *.dSYM to gitignore

These are automatically generated on Mac OS X
Merge pull request #217 from neffs/master

small changes for Mac OS X
Merge pull request #218 from sauttefk/e6-upstream2

make tftp work when TFTP_CRC_SUPPORT is enabled and no format string is ...