Clean 'shadowed declaration' warnings

index is a function in string.h, so replace index with idx all over the
source code.
diff --git a/libkmod/libkmod-index.c b/libkmod/libkmod-index.c
index 3d697d6..3fb736d 100644
--- a/libkmod/libkmod-index.c
+++ b/libkmod/libkmod-index.c
@@ -528,10 +528,10 @@
 	return new;
 }
 
-void index_file_close(struct index_file *index)
+void index_file_close(struct index_file *idx)
 {
-	fclose(index->file);
-	free(index);
+	fclose(idx->file);
+	free(idx);
 }
 
 
diff --git a/libkmod/libkmod.c b/libkmod/libkmod.c
index df75e70..ce7ef3c 100644
--- a/libkmod/libkmod.c
+++ b/libkmod/libkmod.c
@@ -275,7 +275,7 @@
 {
 	char *fn;
 	int err, nmatch = 0, i;
-	struct index_file *index;
+	struct index_file *idx;
 	struct index_value *realnames, *realname;
 	struct kmod_list *l;
 
@@ -284,13 +284,13 @@
 
 	DBG(ctx, "file=%s name=%s\n", fn, name);
 
-	index = index_file_open(fn);
-	if (index == NULL) {
+	idx = index_file_open(fn);
+	if (idx == NULL) {
 		free(fn);
 		return -ENOSYS;
 	}
 
-	realnames = index_searchwild(index, name);
+	realnames = index_searchwild(idx, name);
 	for (realname = realnames; realname; realname = realnames->next) {
 		struct kmod_module *mod;
 
@@ -305,7 +305,7 @@
 	}
 
 	index_values_free(realnames);
-	index_file_close(index);
+	index_file_close(idx);
 	free(fn);
 
 	return nmatch;
@@ -342,7 +342,7 @@
 						struct kmod_list **list)
 {
 	char *fn, *line, *p;
-	struct index_file *index;
+	struct index_file *idx;
 	int n = 0;
 
 	/*
@@ -357,13 +357,13 @@
 
 	DBG(ctx, "file=%s modname=%s\n", fn, name);
 
-	index = index_file_open(fn);
-	if (index == NULL) {
+	idx = index_file_open(fn);
+	if (idx == NULL) {
 		free(fn);
 		return -ENOSYS;
 	}
 
-	line = index_search(index, name);
+	line = index_search(idx, name);
 	if (line != NULL) {
 		struct kmod_module *mod;
 
@@ -379,7 +379,7 @@
 
 finish:
 	free(line);
-	index_file_close(index);
+	index_file_close(idx);
 	free(fn);
 
 	return n;