New MACROs; added sizeof(char) to mem funcs; internal functions marked static;

Marked internal functions as static

Added marcos for:
 strbuf_dup(sb)
 strbuf_append(s1,s2),
 strbuf_append_str(s1,s2)
 strbuf_append_buff(s1,s2)

all memory functions now use sizeof(char) to add support of wide characters