Success with MinGW and AVR and LTO - almost

[Andrew Hutchinson]

I have just succeed in building last snapshot version 4.5.0 20100107 for 
AVR target with working LTO  on both LINUX and MinGW hosts!

As noted before #define LINKER_NAME has to be deleted from target avr.h 
(I will raise patch for this)

I also built avr target for MINGW under MSYS and this has no obvious 
issues for either build or use with normal (non-lto) compilation
However, LTO use failed completely.

LTO using libelf needs to handle files as BINARY with Windows. This 
would seem to  apply to any target on MinGW

I hacked fopen/open calls in  lto.c and lto-elf.c to use O_BINARY and 
"rb" and compilation with -flto was then successful!

I am not sure how this should be fixed properly.

Andy