c-decl.c, [...]: Fix comment typos and formatting.

	* c-decl.c, c-ppoutput.c, combine.c, cppfiles.c, dwarf2out.c,
	expr.c, fold-const.c, gcc.c, haifa-sched.c, loop-iv.c,
	params.def, read-rtl.c, rtl.c, rtlanal.c, toplev.c: Fix
	comment typos and formatting.  Follow spelling conventions.

From-SVN: r78555