Fix indentation (and clang warning) in c-lang.c

I see this warning when building with clang:

      CXX    c-lang.o
    /home/smarchi/src/binutils-gdb/gdb/c-lang.c:314:7: error: misleading indentation; statement is not part of the previous 'if' [-Werror,-Wmisleading-indentation]
          *length = i * width;
          ^
    /home/smarchi/src/binutils-gdb/gdb/c-lang.c:308:4: note: previous statement is here
              if (extract_unsigned_integer (contents + i * width,
              ^

It took me a while to notice that some lines in that area have a
spurious space before the tabs, at the beginning of the ling.  I'm not
sure how clang translates that to misleading indentation, but making the
indentation correct gets rid of the error.

There are many more instances of this in the code base (`grep -P '^ \t'
*.c`), if others think it's a good idea, it would be pretty easy to fix
them all up in one shot.

gdb/ChangeLog:

	* c-lang.c (c_get_string, asm_language_defn): Remove space
	before tab.