PPC error/warning messages

PPC error/warning messages

The GNU coding standard says error messages should be of the form
  program:sourcefile:lineno: message
or
  program: message

and
"The string message should not begin with a capital letter when it
follows a program name and/or file name, because that isn’t the
beginning of a sentence. (The sentence conceptually starts at the
beginning of the line.) Also, it should not end with a period."

This patch does that for ppc, and removes some British spelling.
I've also switched some error output from using the linker callback
einfo to _bfd_error_handler, due to improved compilation time
argument checking now done for the latter function.

bfd/
	* elf32-ppc.c: Standardize error/warning messages.  Use
	_bfd_error_handler rather than einfo when einfo features not used.
	* elf64-ppc.c: Likewise.
ld/
	* testsuite/ld-powerpc/attr-gnu-12-21.d: Update.
	* testsuite/ld-powerpc/attr-gnu-4-12.d: Update.
	* testsuite/ld-powerpc/attr-gnu-4-13.d: Update.
	* testsuite/ld-powerpc/attr-gnu-4-21.d: Update.
	* testsuite/ld-powerpc/attr-gnu-4-23.d: Update.
	* testsuite/ld-powerpc/attr-gnu-4-31.d: Update.
	* testsuite/ld-powerpc/attr-gnu-4-32.d: Update.
	* testsuite/ld-powerpc/attr-gnu-8-23.d: Update.