x86:  fix 'Error: .size expression for idle_stack does not evaluate to a constant' bug from Matt Campbell

Assembler changes with the gcc-47 distribution from ARM mean that we need to be explicit about branch one or more of the wide branch opcodes results in bad table branching.  From Mike Smith

configs/efm32-dk3650: Support for Energy Micro's development kit for the Leopard Gecko MCU.  From Richard Cochran

arch/arm/src/Makefile: dependency directory list is now computed from the VPATH.  From Richard Cochran

Config.mk: If WINTOOL is set, COMPILE definition should convert path generated by Cygwin make to a proper Windows path.  From Richard Cochran (2014-1-23).