IMPORT: sha1: import SHA1 functions

This is based on the git SHA1 implementation and optimized to do word
accesses rather than byte accesses, and to avoid unnecessary copies into
the context array.
diff --git a/Makefile b/Makefile
index f3e6976..ed93d29 100644
--- a/Makefile
+++ b/Makefile
@@ -842,7 +842,7 @@
        src/regex.o src/queue.o src/frontend.o src/arg.o src/proto_uxst.o \
        src/raw_sock.o src/lb_chash.o src/lb_fwlc.o src/lb_fwrr.o \
        src/lb_fas.o src/applet.o src/hdr_idx.o src/ev_select.o src/hash.o \
-       src/lb_map.o src/base64.o src/protocol.o src/h1.o
+       src/lb_map.o src/base64.o src/sha1.o src/protocol.o src/h1.o
 
 EBTREE_OBJS = $(EBTREE_DIR)/ebtree.o \
               $(EBTREE_DIR)/eb32tree.o $(EBTREE_DIR)/eb64tree.o \