Math/Screen: fix coding style
Math/Screen: remove useless optimized scale==100 special case

Integer multiplication is fast enough.  May be as fast as the
"if/else".
Math/Screen: remove ineffective sin/cos cache

Angle::ifastsine() and Angle::ifastcosine() are just a simple table
lookup.  Tests have shown that PolygonRotateShift()'s cache hits
rarely anyway.

This makes PolygonRotateShift() thread-safe.
Math/Screen: remove useless Angle::AsBearing() call
Math/Screen: pass RasterPoint to PolygonRotateShift()
Screen/Layout: add unsigned Scale() overloads
Math/Screen: use Layout::FastScale()

Eliminate duplicate code.
link.mk: Add _NO_LIB_PREFIX option to link-shared-library function
python.mk: Use link-shared-library instead of link-python-library
link.mk: Don't add incompatible linker flags if HOST_IS_DARWIN
python.mk: Use python-config to add the right includes and ldlibs
Makefile: drop clang option "-integrated-as"

Appears not to be necessary anymore with clang 3.5.
Makefile: drop duplicate "-march=armv6" option for TARGET=PI
Makefile: add variable TARGET_IS_ARMHF

Controls the compiler option "-mfloat-abi=hard".
Makefile: move TARGET_IS_LINUX up

Make it available earlier.
Makefile: use "arm-linux-gnueabi(hf)" for clang/ARM

Instead of specifying the ARMv6/ARMv7 architecture in the "clang
-target" option, use the classic "-march=" flag.  Use a "-target" with
just "arm", so clang can find the linker (there is no ARMv6/ARMv7
specific linker).
Screen/Layout: add unsigned FastScale() overloads
AirspaceListRenderer: don't use PixelScalar
AirspaceListRenderer: cache Layout::FastScale(4)
Dialogs/TaskEditPanel: don't use PixelScalar