doxygen docs: Add missing group braces

Without them, these Evil docs had no group and therefore didn't appear anywhere.

src/lib/evil/evil_stdio.h

@@ -9,7 +9,7 @@
  * @ingroup Evil
  *
  * This header provides functions ported from Unix in stdio.h.
- *
+ * @{
  */
 
 #define EVIL_PATH_SEP_SWAP(p, s1, s2) \
@@ -56,5 +56,8 @@ EAPI int evil_rename(const char *src, const char *dst);
  */
 EAPI int evil_mkdir(const char *dirname, mode_t mode);
 
+/**
+ * @}
+ */
 
 #endif /* __EVIL_STDIO_H__ */

src/lib/evil/evil_string.h

@@ -10,7 +10,7 @@
  *
  * This header provides functions ported from Unix in string.h.
  *
- *
+ * @{
  */
 
 
@@ -63,4 +63,8 @@ EAPI char *strcasestr(const char *haystack, const char *needle);
  */
 EAPI char *strsep(char **stringp, const char *delim);
 
+/**
+ * @}
+ */
+
 #endif /* __EVIL_STRING_H__ */