1.5.6: More SN64 tweaks and data/rodata endianess

Fixes data analyzis. It was ignoring banned symbols
Use .rdata on rodata migration for SN64
Fix ASM_DATA_SYM_AS_LABEL on bss generation
Fix rodata symbols searching during migration
Add option to disassemble data/rodata with different endianess than the global one
Allow changing the string encoding per rodata segment
Return the created segment by addOverlaySegment

Decompollaborate / spimdisasm