buildgcc: Update coreboot reference toolchain to gcc 4.6.2

buildgcc: Update coreboot reference toolchain to gcc 4.6.2

In addition:
- drop some unneeded patches
- make the scripting support depend on SKIPPYTHON not SKIPGDB
  so it is possible to build GDB with and without scripting support
- rename the repository checkout version of GCC trunk, not X+1
  so we don't have to change it on every version upgrade.

Change-Id: I1b7d5b8921187c1c1d39b04f20bb715ddba72fe8
Signed-off-by: Stefan Reinauer <reinauer@google.com>
Reviewed-on: http://review.coreboot.org/367
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>