added strconcat and strcpy functions

strconcat.sl

@@ -0,0 +1,70 @@
+import stdlib/stdlib.sl
+import stdlib/io.sl
+
+: strconcat
+    0 pick 3 pick +
+    >r >r >r >r >r
+    8 alloc
+    r> r>
+    dup >r
+    strcpy
+    swap
+    r> dup -rot +
+    r> r>
+    strcpy
+    swap
+    3 pick
+    -
+    swap
+    drop
+    swap
+    0 rpick
+    nip
+;
+
+: alloc
+    0      # addr hint (NULL)
+    swap   # size
+    3      # prot (PROT_READ | PROT_WRITE)
+    34     # flags (MAP_PRIVATE | MAP_ANON)
+    -1     # fd
+    0      # offset
+    mmap
+;
+
+: free
+    munmap drop
+;
+
+: strcpy #(dst_addr src_addr len -- dst_addr len)
+    dup
+    >r
+    swap
+    dup c@
+    3 pick swap
+    c!
+    drop
+    swap
+    for
+        1 + dup
+        c@
+        swap
+        -rot
+        swap
+        1 +
+        dup
+        rot
+        c!
+        drop
+        swap
+    next
+    swap
+    nip
+    r> dup -rot - swap
+;
+
+: main
+    "hello " "world"
+    strconcat
+    puts
+;