remove redundant redeclarations

All three functions gave similar warning, here is a sample who the
message text looked.

src/libabc.c:236:24: warning: redundant redeclaration of 'abc_list_entry_get_next' [-Wredundant-decls]
 struct abc_list_entry *abc_list_entry_get_next(struct abc_list_entry *list_entry);
                        ^
In file included from src/libabc.c:30:0:
./src/abc/libabc.h:55:24: note: previous declaration of 'abc_list_entry_get_next' was here
 struct abc_list_entry *abc_list_entry_get_next(struct abc_list_entry *list_entry);

1 files changed, 0 insertions, 3 deletions

diff --git a/src/libabc.c b/src/libabc.c
index c3c1fef..23fdcd5 100644
--- a/src/libabc.c
+++ b/src/libabc.c
@@ -233,9 +233,6 @@ ABC_EXPORT void abc_set_log_priority(struct abc_ctx *ctx, int priority)
 }
 
 struct abc_list_entry;
-struct abc_list_entry *abc_list_entry_get_next(struct abc_list_entry *list_entry);
-const char *abc_list_entry_get_name(struct abc_list_entry *list_entry);
-const char *abc_list_entry_get_value(struct abc_list_entry *list_entry);
 
 struct abc_thing {
         struct abc_ctx *ctx;