Remove tabs from libvirt_public.syms & enforce it

* src/libvirt_public.syms: Death to tabs
* cfg.mk: Check .syms files for tabs

cfg.mk

@@ -413,11 +413,11 @@ sc_prohibit_ctype_h:
 # Ensure that no C source file, docs, or rng schema uses TABs for
 # indentation.  Also match *.h.in files, to get libvirt.h.in.  Exclude
 # files in gnulib, since they're imported.
-space_indent_files=(\.(rng|s?[ch](\.in)?|html.in|py)|(daemon|tools)/.*\.in)
+space_indent_files=(\.(rng|s?[ch](\.in)?|html.in|py|syms)|(daemon|tools)/.*\.in)
 sc_TAB_in_indentation:
 	@prohibit='^ *	'						\
 	in_vc_files='$(space_indent_files)$$'				\
-	halt='indent with space, not TAB, in C, sh, html, py, and RNG schemas' \
+	halt='indent with space, not TAB, in C, sh, html, py, syms and RNG schemas' \
 	  $(_sc_search_regexp)
 
 ctype_re = isalnum|isalpha|isascii|isblank|iscntrl|isdigit|isgraph|islower\