[RFA] testsuite/gdb.arch/i386-prologue.c: Fix compiling on Cygwin

[Michael Elizabeth Chastain]

Same response as i386-prologue.c.  I would like to see:

  "   call " SP_PREFIX "trap\n"
  "   .globl " SP_PREFIX "main\n"

Or a similar design with

  "   call " SYMBOL(trap) "\n"
  "   .globl " SYMBOL(main) "\n"

Michael C

===

	* gdb.arch/i386-unwind.c: Conditionalize label names to build
	on Cygwin.