modernized mcs51 backend

Binutils 2.45.1 MCS-51 Port

Key Changes to Binutils 2.45.1:

• Migrated from 'elf' to 'generic' template
• Created custom ld/scripttempl/elf32i51.sc with MCS-51 MEMORY regions
• Implemented compiler-independent weak symbols ( __gsinit_startup, __external_startup, __init_data )

refs:

• http://web51.hw.cz/
• https://github.com/github0null/binutils-mcs51
• https://github.com/volumit/sdcc_aurix_scr_42

intelligence assisted

mcs51 backend

patch from http://web51.hw.cz