Add linux-arm64 reg profile, fix linux-arm systracing. Handle multiple syscall stoppers in 'dcs'
Fix build and some scary warnings in RCoreFile->fd
travis: split tests to multiple jobs / fail only on regressions
a few cleanups in bin and lang

* libr/bin/bin.c: remove duplicate condition (xtr && xtr)
* libr/bin/p/bin_elf.c!libs: use r_list_newf
* libr/lang/p/Makefile: add empty "clean" target to silence make warning
Refix 'dcs' and enhace '?' colorized help
Fix 'make dist'
Show warning when trying to disable the sandbox
Disable debugger commands in sandbox mode
Disable 'pwd' and 'ls' in sandbox mode
Show warning if sandbox enabled in '|' and fix the "funny" 'ls|less' bug
Fix empty graph calls nodes (exposes bug in xref analysis)
Add orange-gray theme (ogray). Move doc/r2theme to shlr/www/enyo/colors