ARM and AArch64 messages

ARM and AArch64 messages

More standarization of error/warning messages.  The ARM backend has
some multi-line error messages, which don't fit particularly well with
the GNU coding standard insistence that error messages shouldn't be
capitalized or have a full-stop.  I've replaced the line breaks with
semicolons.

So for instance the following
  system/path/to/ld: myobject.o: invalid special symbol `foo'.
  system/path/to/ld: It must be a global or weak function symbol.
becomes
  system/path/to/ld: myobject.o: invalid special symbol `foo'; it must be a global or weak function symbol

bfd/
	* elf32-arm.c, * elfnn-aarch64.c: Standardize error/warning messages.
ld/
	* testsuite/ld-aarch64/reloc-overflow-bad.d,
	* testsuite/ld-arm/attr-merge-9.out,
	* testsuite/ld-arm/attr-merge-arch-2.d,
	* testsuite/ld-arm/attr-merge-unknown-1.d,
	* testsuite/ld-arm/attr-merge-unknown-2.d,
	* testsuite/ld-arm/attr-merge-unknown-2r.d,
	* testsuite/ld-arm/attr-merge-unknown-3.d,
	* testsuite/ld-arm/cmse-implib-errors.out,
	* testsuite/ld-arm/cmse-new-earlier-later-implib.out,
	* testsuite/ld-arm/cmse-new-implib-no-output.out,
	* testsuite/ld-arm/cmse-new-implib-not-sg-in-implib.out,
	* testsuite/ld-arm/cmse-new-implib.out,
	* testsuite/ld-arm/cmse-new-wrong-implib.out,
	* testsuite/ld-arm/cmse-veneers-no-gnu_sgstubs.out,
	* testsuite/ld-arm/cmse-veneers-wrong-entryfct.out,
	* testsuite/ld-arm/group-relocs-alu-bad-2.d,
	* testsuite/ld-arm/group-relocs-alu-bad.d,
	* testsuite/ld-arm/group-relocs-ldc-bad-2.d,
	* testsuite/ld-arm/group-relocs-ldc-bad.d,
	* testsuite/ld-arm/group-relocs-ldr-bad-2.d,
	* testsuite/ld-arm/group-relocs-ldr-bad.d,
	* testsuite/ld-arm/group-relocs-ldrs-bad-2.d,
	* testsuite/ld-arm/group-relocs-ldrs-bad.d,
	* testsuite/ld-arm/stm32l4xx-cannot-fix-far-ldm.d: Update.