REORG: include: move ist.h from common/ to import/

Fortunately that file wasn't made dependent upon haproxy since it was
integrated, better isolate it before it's too late. Its dependency on
api.h was the result of the change from config.h, which in turn wasn't
correct. It was changed back to stddef.h for size_t and sys/types.h for
ssize_t. The recently added reference to MAX() was changed as it was
placed only to avoid a zero length in the non-free-standing version and
was causing a build warning in the hpack encoder.
diff --git a/src/debug.c b/src/debug.c
index 7f281f0..e1b9070 100644
--- a/src/debug.c
+++ b/src/debug.c
@@ -23,7 +23,7 @@
 #include <common/buf.h>
 #include <common/debug.h>
 #include <common/hathreads.h>
-#include <common/ist.h>
+#include <import/ist.h>
 #include <common/net_helper.h>
 #include <common/standard.h>
 
diff --git a/src/h2.c b/src/h2.c
index 891c3e0..c94ea8e 100644
--- a/src/h2.c
+++ b/src/h2.c
@@ -29,7 +29,7 @@
 #include <haproxy/api.h>
 #include <common/h2.h>
 #include <common/http-hdr.h>
-#include <common/ist.h>
+#include <import/ist.h>
 #include <types/global.h>
 
 struct h2_frame_definition h2_frame_definition[H2_FT_ENTRIES] =	{
diff --git a/src/hpack-dec.c b/src/hpack-dec.c
index fa25ac4..50293d8 100644
--- a/src/hpack-dec.c
+++ b/src/hpack-dec.c
@@ -36,7 +36,7 @@
 #include <common/hpack-tbl.h>
 #include <common/chunk.h>
 #include <common/h2.h>
-#include <common/ist.h>
+#include <import/ist.h>
 
 #include <types/global.h>
 
diff --git a/src/hpack-enc.c b/src/hpack-enc.c
index 1a6fa1c..bf7336b 100644
--- a/src/hpack-enc.c
+++ b/src/hpack-enc.c
@@ -32,7 +32,7 @@
 
 #include <common/hpack-enc.h>
 #include <common/http-hdr.h>
-#include <common/ist.h>
+#include <import/ist.h>
 
 #include <types/global.h>
 
diff --git a/src/hpack-tbl.c b/src/hpack-tbl.c
index effe5e0..31c24b2 100644
--- a/src/hpack-tbl.c
+++ b/src/hpack-tbl.c
@@ -32,7 +32,7 @@
 
 #include <common/hpack-huff.h>
 #include <common/hpack-tbl.h>
-#include <common/ist.h>
+#include <import/ist.h>
 
 #include <types/global.h>
 
diff --git a/src/mux_fcgi.c b/src/mux_fcgi.c
index 5ce6f61..7ff3932 100644
--- a/src/mux_fcgi.c
+++ b/src/mux_fcgi.c
@@ -15,7 +15,7 @@
 #include <common/fcgi.h>
 #include <common/h1.h>
 #include <common/htx.h>
-#include <common/ist.h>
+#include <import/ist.h>
 #include <common/mini-clist.h>
 #include <common/net_helper.h>
 
diff --git a/src/sink.c b/src/sink.c
index 20d3d79..7eb283f 100644
--- a/src/sink.c
+++ b/src/sink.c
@@ -20,7 +20,7 @@
 
 #include <haproxy/api.h>
 #include <common/cfgparse.h>
-#include <common/ist.h>
+#include <import/ist.h>
 #include <common/mini-clist.h>
 #include <common/time.h>
 #include <proto/cli.h>
diff --git a/src/trace.c b/src/trace.c
index 667cd81..3f6ff05 100644
--- a/src/trace.c
+++ b/src/trace.c
@@ -20,7 +20,7 @@
 
 #include <haproxy/api.h>
 #include <common/buffer.h>
-#include <common/ist.h>
+#include <import/ist.h>
 #include <common/mini-clist.h>
 #include <proto/cli.h>
 #include <proto/log.h>