* config/tc-i860.c: Remove SYNTAX_SVR4 macro and occurrences.
(target_intel_syntax): Declare variable.
(OPTION_INTEL_SYNTAX): Declare macro.
(md_longopts): Add option -mintel-syntax.
(md_parse_option): Set target_intel_syntax.
(md_show_usage): Add -mintel-syntax usage.
(md_begin): Set reg_prefix based on target_intel_syntax.
(i860_process_insn): Skip register prefix only if there is one.
Parse relocatable expressions in either Intel or AT&T syntax based
on target_intel_syntax instead of the SYNTAX_SVR4 macro.
* doc/c-i860.texi: Document -mintel-syntax option and give blurb
about the differences in syntax.