REORG: http: move some very http1-specific parts to h1.{c,h}

Certain types and enums are very specific to the HTTP/1 parser, and we'll
need to share them with the HTTP/2 to HTTP/1 translation code. Let's move
them to h1.c/h1.h. Those with very few occurrences or only used locally
were renamed to explicitly mention the relevant HTTP version :

  enum ht_state      -> h1_state.
  http_msg_state_str -> h1_msg_state_str
  HTTP_FLG_*         -> H1_FLG_*
  http_char_classes  -> h1_char_classes

Others like HTTP_IS_*, HTTP_MSG_* are left to be done later.
diff --git a/Makefile b/Makefile
index ddc32df..f3e6976 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/lb_map.o src/base64.o src/protocol.o src/h1.o
 
 EBTREE_OBJS = $(EBTREE_DIR)/ebtree.o \
               $(EBTREE_DIR)/eb32tree.o $(EBTREE_DIR)/eb64tree.o \