Revert "Makefile: change some optimizations"

This reverts commit fa6e10dab21628b92df354fdced69e9bd0e4c6c2.
Fix compiling for GCC 4.6
Lower FSB overclock
Fix voltage limits
Min voltage: 700mV Max voltage: 1400mV
Change default 2D GPU frequency to 200MHz
Makefile: allow building with custom toolchains
Build script: change toolchain path