Enabled Swing Modulo Scheduling

-fmodulo-sched and -fmodulo-sched-allow-regmoves are fairly new optimizations not currently automatically enabled at any -O level.
These options improve loop scheduling – more information can be found there: https://gcc.gnu.org/news/sms.html.

Change-Id: I69b3fa05e0d5d262ddbe5ec5da0ba0573b1db38a

Conflicts:
	core/combo/select.mk
clang:updated unknown cflags

-fmodulo-sched and -fmodulo-sched-allow-regmoves are not supported by clang, so we need to add them to the unknown flag list

Change-Id: I75b8b4b62732f1a8f006e25127b8edadaf976920

Conflicts:
	core/clang/config.mk