Fix non-aligned CodeView symbols

CodeView symbols in PDB files are aligned to four-byte boundaries. It's
not really clear what logic MSVC uses to enforce this; sometimes the
symbols are padded in the object file, sometimes the linker seems to do
the work.

It makes more sense to do this in the compiler, so fix the two instances
where we can write symbols with a non-aligned length. S_FRAMEPROC is
unusually not a multiple of 4, so will always have 2 bytes padding.
S_INLINESITE is followed by variable-length "binary annotations", so
will also usually have padding.

gcc/
	* dwarf2codeview.cc (write_s_frameproc): Align output.
	(write_s_inlinesite): Align output.