Add HTTP request parsing.

This extends the existing http parser to support requests as well as responses.

httpcli continues to exist and work as it has previously, though in the new
directory src/core/http (to reflect the fact the directory now contains code
relevant to parsing requests, which httpcli would not generally involve itself
in).
diff --git a/BUILD b/BUILD
index 2c2cce7..4ca2c25 100644
--- a/BUILD
+++ b/BUILD
@@ -190,9 +190,9 @@
     "src/core/compression/algorithm_metadata.h",
     "src/core/compression/message_compress.h",
     "src/core/debug/trace.h",
-    "src/core/httpcli/format_request.h",
-    "src/core/httpcli/httpcli.h",
-    "src/core/httpcli/parser.h",
+    "src/core/http/format_request.h",
+    "src/core/http/httpcli.h",
+    "src/core/http/parser.h",
     "src/core/iomgr/closure.h",
     "src/core/iomgr/endpoint.h",
     "src/core/iomgr/endpoint_pair.h",
@@ -331,9 +331,9 @@
     "src/core/compression/compression_algorithm.c",
     "src/core/compression/message_compress.c",
     "src/core/debug/trace.c",
-    "src/core/httpcli/format_request.c",
-    "src/core/httpcli/httpcli.c",
-    "src/core/httpcli/parser.c",
+    "src/core/http/format_request.c",
+    "src/core/http/httpcli.c",
+    "src/core/http/parser.c",
     "src/core/iomgr/closure.c",
     "src/core/iomgr/endpoint.c",
     "src/core/iomgr/endpoint_pair_posix.c",
@@ -429,7 +429,7 @@
     "src/core/transport/static_metadata.c",
     "src/core/transport/transport.c",
     "src/core/transport/transport_op_string.c",
-    "src/core/httpcli/httpcli_security_connector.c",
+    "src/core/http/httpcli_security_connector.c",
     "src/core/security/b64.c",
     "src/core/security/client_auth_filter.c",
     "src/core/security/credentials.c",
@@ -562,9 +562,9 @@
     "src/core/compression/algorithm_metadata.h",
     "src/core/compression/message_compress.h",
     "src/core/debug/trace.h",
-    "src/core/httpcli/format_request.h",
-    "src/core/httpcli/httpcli.h",
-    "src/core/httpcli/parser.h",
+    "src/core/http/format_request.h",
+    "src/core/http/httpcli.h",
+    "src/core/http/parser.h",
     "src/core/iomgr/closure.h",
     "src/core/iomgr/endpoint.h",
     "src/core/iomgr/endpoint_pair.h",
@@ -690,9 +690,9 @@
     "src/core/compression/compression_algorithm.c",
     "src/core/compression/message_compress.c",
     "src/core/debug/trace.c",
-    "src/core/httpcli/format_request.c",
-    "src/core/httpcli/httpcli.c",
-    "src/core/httpcli/parser.c",
+    "src/core/http/format_request.c",
+    "src/core/http/httpcli.c",
+    "src/core/http/parser.c",
     "src/core/iomgr/closure.c",
     "src/core/iomgr/endpoint.c",
     "src/core/iomgr/endpoint_pair_posix.c",
@@ -1390,9 +1390,9 @@
     "src/core/compression/compression_algorithm.c",
     "src/core/compression/message_compress.c",
     "src/core/debug/trace.c",
-    "src/core/httpcli/format_request.c",
-    "src/core/httpcli/httpcli.c",
-    "src/core/httpcli/parser.c",
+    "src/core/http/format_request.c",
+    "src/core/http/httpcli.c",
+    "src/core/http/parser.c",
     "src/core/iomgr/closure.c",
     "src/core/iomgr/endpoint.c",
     "src/core/iomgr/endpoint_pair_posix.c",
@@ -1488,7 +1488,7 @@
     "src/core/transport/static_metadata.c",
     "src/core/transport/transport.c",
     "src/core/transport/transport_op_string.c",
-    "src/core/httpcli/httpcli_security_connector.c",
+    "src/core/http/httpcli_security_connector.c",
     "src/core/security/b64.c",
     "src/core/security/client_auth_filter.c",
     "src/core/security/credentials.c",
@@ -1566,9 +1566,9 @@
     "src/core/compression/algorithm_metadata.h",
     "src/core/compression/message_compress.h",
     "src/core/debug/trace.h",
-    "src/core/httpcli/format_request.h",
-    "src/core/httpcli/httpcli.h",
-    "src/core/httpcli/parser.h",
+    "src/core/http/format_request.h",
+    "src/core/http/httpcli.h",
+    "src/core/http/parser.h",
     "src/core/iomgr/closure.h",
     "src/core/iomgr/endpoint.h",
     "src/core/iomgr/endpoint_pair.h",