GCC warnings

[EugeneZelenko]

I think will be good idea to fix next GCC warnings:

linenoiseHistoryAdd() is defined in linenoise.h.

If functions without prototypes in linenoise.h are not intended to be used outside linenoise.c they should be made static.

Compiling C file linenoise.c (debug + pic)
linenoise.c:173:5: warning: redundant redeclaration of 'linenoiseHistoryAdd' [-Wredundant-decls]
int linenoiseHistoryAdd(const char *line);
^
In file included from linenoise.c:117:0:
linenoise.h:54:5: note: previous declaration of 'linenoiseHistoryAdd' was here
int linenoiseHistoryAdd(const char *line);
^
linenoise.c:594:5: warning: no previous prototype for 'linenoiseEditInsert' [-Wmissing-prototypes]
int linenoiseEditInsert(struct linenoiseState *l, char c) {
^
linenoise.c:621:6: warning: no previous prototype for 'linenoiseEditMoveLeft' [-Wmissing-prototypes]
void linenoiseEditMoveLeft(struct linenoiseState *l) {
^
linenoise.c:629:6: warning: no previous prototype for 'linenoiseEditMoveRight' [-Wmissing-prototypes]
void linenoiseEditMoveRight(struct linenoiseState *l) {
^
linenoise.c:637:6: warning: no previous prototype for 'linenoiseEditMoveHome' [-Wmissing-prototypes]
void linenoiseEditMoveHome(struct linenoiseState *l) {
^
linenoise.c:645:6: warning: no previous prototype for 'linenoiseEditMoveEnd' [-Wmissing-prototypes]
void linenoiseEditMoveEnd(struct linenoiseState *l) {
^
linenoise.c:656:6: warning: no previous prototype for 'linenoiseEditHistoryNext' [-Wmissing-prototypes]
void linenoiseEditHistoryNext(struct linenoiseState *l, int dir) {
^
linenoise.c:680:6: warning: no previous prototype for 'linenoiseEditDelete' [-Wmissing-prototypes]
void linenoiseEditDelete(struct linenoiseState *l) {
^
linenoise.c:690:6: warning: no previous prototype for 'linenoiseEditBackspace' [-Wmissing-prototypes]
void linenoiseEditBackspace(struct linenoiseState *l) {
^
linenoise.c:702:6: warning: no previous prototype for 'linenoiseEditDeletePrevWord' [-Wmissing-prototypes]
void linenoiseEditDeletePrevWord(struct linenoiseState *l) {