gdb.trace/tfile.c: Remove Thumb bit in one more more, general cleanup

gdb.trace/tfile.c: Remove Thumb bit in one more more, general cleanup

I noticed that the existing code casts a function's address to 'long',
but that doesn't work correctly on some ABIs, like Win64, where long
is 32-bit and while pointers are 64-bit:

  func_addr = (long) &write_basic_trace_file;

Fixing that showed there's actually another place in the file that
writes a function address to file, and therefore should clear the
Thumb bit.  This commit adds a macro+function pair to centralize the
Thumb bit handling, and uses it in both places.

The rest is just enough changes to make the file build without
warnings with "-Wall -Wextra" with x86_64-w64-mingw32-gcc and
i686-w64-mingw32-gcc cross compilers, and with -m32/-m64 on x86_64
GNU/Linux.  Currently with x86_64-w64-mingw32-gcc we get:

  $ x86_64-w64-mingw32-gcc tfile.c  -Wall -DTFILE_DIR=\"\"
  tfile.c: In function 'start_trace_file':
  tfile.c:51:23: error: 'S_IRGRP' undeclared (first use in this function)
	 S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH);
			 ^
  tfile.c:51:23: note: each undeclared identifier is reported only once for each function it appears in
  tfile.c:51:31: error: 'S_IROTH' undeclared (first use in this function)
	 S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH);
				 ^
  tfile.c: In function 'add_memory_block':
  tfile.c:79:10: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
     ll_x = (unsigned long) addr;
	    ^
  tfile.c: In function 'write_basic_trace_file':
  tfile.c:113:15: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
     func_addr = (long) &write_basic_trace_file;
		 ^
  tfile.c:137:3: warning: passing argument 1 of 'add_memory_block' from incompatible pointer type [enabled by default]
     add_memory_block (&testglob, sizeof (testglob));
     ^
  tfile.c:72:1: note: expected 'char *' but argument is of type 'int *'
   add_memory_block (char *addr, int size)
   ^
  tfile.c:139:3: warning: passing argument 1 of 'add_memory_block' from incompatible pointer type [enabled by default]
     add_memory_block (&testglob2, 1);
     ^
  tfile.c:72:1: note: expected 'char *' but argument is of type 'int *'
   add_memory_block (char *addr, int size)
   ^
  tfile.c: In function 'write_error_trace_file':
  tfile.c:185:3: warning: implicit declaration of function 'alloca' [-Wimplicit-function-declaration]
     char *hex = alloca (len * 2 + 1);
     ^
  tfile.c:185:15: warning: incompatible implicit declaration of built-in function 'alloca' [enabled by default]
     char *hex = alloca (len * 2 + 1);
		 ^
  tfile.c:211:6: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
	(long) &write_basic_trace_file);
      ^

Tested on x86_64 Fedora 20, -m64 and -m32.
Tested by Yao on arm targets.

gdb/testsuite/
2014-07-16  Pedro Alves  <palves@redhat.com>

	* gdb.trace/tfile.c: Include unistd.h and stdint.h.
	(start_trace_file): Guard S_IRGRP and S_IROTH uses behind #ifdef.
	(tfile_write_64, tfile_write_16, tfile_write_8, tfile_write_addr)
	(tfile_write_buf): New functions.
	(add_memory_block): Rewrite using the above.
	(adjust_function_address): New function.
	(FUNCTION_ADDRESS): New macro.
	(write_basic_trace_file): Remove short_x local, and use
	tfile_write_16. Change type of func_addr local to unsigned long
	long.  Use FUNCTION_ADDRESS instead of handling the Thumb bit
	here.  Cast argument of add_memory_block to char pointer.
	(write_error_trace_file): Avoid alloca.  Use FUNCTION_ADDRESS.
	(main): Remove parameters.
	* gdb.trace/tfile.exp: Remove nowarnings.