[nautilus] eel-string: Add description to some eel-string functions

[Ernestas Kulik <ernestask src gnome org>]

commit d4983562d6825fa47ae81bdcabc8b0cea0e498d5
Author: ionbabalau <ionel_babalau yahoo com>
Date:   Sun Oct 21 16:42:09 2018 +0300

    eel-string: Add description to some eel-string functions
    
    The eel_str_double_underscores and eel_str_capitalize
    functions didn't have documentation.
    Added importance of eel_str_double_underscores as well.
    
    It's good practice to have documentation for functions
    in the long term.

 eel/eel-string.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)
---
diff --git a/eel/eel-string.c b/eel/eel-string.c
index 1fa480c24..077c1c379 100644
--- a/eel/eel-string.c
+++ b/eel/eel-string.c
@@ -33,6 +33,18 @@
 #include "eel-lib-self-check-functions.h"
 #endif
 
+/**
+ * eel_str_double_underscores:
+ * @string: input string
+ *
+ * This is used if you want to preserve underscore characters
+ * when creating a label with gtk_label_new_with_mnemonic().
+ *
+ * Returns: a newly allocated copy of @string,
+ * with a doubled number of underscores.
+ * If @string doesn't contain underscores, returns a copy of it.
+ * If @string is %NULL, returns %NULL.
+ */
 char *
 eel_str_double_underscores (const char *string)
 {
@@ -72,6 +84,14 @@ eel_str_double_underscores (const char *string)
     return escaped;
 }
 
+/**
+ * eel_str_capitalize:
+ * @string: input string
+ *
+ * Returns: a newly allocated copy of @string,
+ * with the first letter capitalized.
+ * If @string is %NULL, returns %NULL.
+ */
 char *
 eel_str_capitalize (const char *string)
 {