Don't redownload already existing files

Aside from saving bandwidth, this saves the script from crashing with a 'permission denied' halfways and having to be restarted
NOW we have all the needed packages here, even those required by psplibraries
Functions for fun and profit
One $ can make all the difference
Now auto_extract works properly in all cases too
Think positive
Oops, those links were pointing to the wrong place
Merged all dependency checks into one file
Added a function to check for aclocal files
Merge branch 'master' of github.com:pspdev/psptoolchain

Conflicts:
	depends/check-autoconf.sh
	depends/check-automake.sh
	depends/check-bison.sh
	depends/check-elf.sh
	depends/check-flex.sh
	depends/check-gcc.sh
	depends/check-git.sh
	depends/check-gmp.sh
	depends/check-libelf.sh
	depends/check-libusb.sh
	depends/check-make.sh
	depends/check-mpc.sh
	depends/check-mpfr.sh
	depends/check-ncurses.sh
	depends/check-patch.sh
	depends/check-readline.sh
	depends/check-subversion.sh
	depends/check-texinfo.sh
	depends/check-wget.sh
	depends/check-zlib.sh
I think this is a complete dependency list
Added a depend script to check if /bin/sh is dash (See #30)
Why is bash syntax so quirky

Apparently && and || has the SAME predecence in bash, and thus ||s can short-circuit entire expressions. Gah.
Prevent git clone from waiting for input at all
Check for libelf/gelf.h and executable bits
Space indentation
Fixed clone_git_repo
Merge pull request #42 from uppfinnarn/master

Various fixes