[lib][libm] initial minimal version of libm, from bionic

Mostly picked up the sin/cos/tan/sqrt routines.

Change-Id: If265b6555336cf049b14d2eb945924f4e9fec225
[arch][arm] add arm specific asm header
[arch][arm] disable VFP in irq mode, add arch_in_int_handler

On IRQ entry, disable the floating point unit. If floating point
code is used inside irq mode the undefined handler will panic.
[kernel] add thread_unblock() in case a thread needs to be directly put into ready state

Also tighten the critical section requirement for some of the deep thread
routines for efficiency purposes.
[app][bench] add some quick n dirty sin/cos/sqrt benchmarks if libm is built
[project][zybo-test] add libm to the build
[libc][printf] first stab at supporting floating point printf

Add support for %a and %A for all floats but denormalized.
[app][tests] tests for floating point printf
[make] properly prefix the spotless path with BUILDROOT

Change-Id: I3cbda4c95751124252bc535a82a78bc6a6c7f8f5
[make] fix the quoting around make spotless rm
[kernel] add real time flag for threads

Threads marked as real time do not have the preemption timer run against
them and will continue to run until they voluntarily yield or are
preempted by a higher priority thread from irq context.
[dev][timer][arm_generic] implementation of generic timer for cortex-a15 and related cores
[gem] Explicitly enable interrupts we care about rather than using a bitmask
[zynq] Remove generated init for Zybo, add platform init routines
[zynq] Add mio command to dump mio state
[zynq] Move zybo-common to zynq-common
[zynq] Add uzed target support
[zynq] Add support to boot without configuring DRAM
[uzed] Add dram test