Copy piqi-ocaml from its external repo

Copy as a subdirectory from https://github.com/alavrik/piqi-ocaml

This is the first step in reintegrating it with the main piqi repo to
unify the OCaml codebase and streamline the logistics for furture
maintenance and use by OCaml users.

More contex in #73

piqi-ocaml/CHANGES

@@ -0,0 +1,119 @@
+Piqi-ocaml 0.7.8 (Aug 05, 2019)
+===============================
+
+- Add support for the dune build system and use it from OPAM by default
+- Switch CI setup from Travis to GH Actions
+
+
+Piqi-ocaml 0.7.7 (Oct 12, 2019)
+===============================
+
+- Switch from Pervasives to Stdlib
+
+
+Piqi-ocaml 0.7.6 (Sep 13, 2018)
+===============================
+
+- Fix sometimes incorrect handling of unknown fields (--gen-preserve-unknown-fields)
+- (new) add support for .internal flag for fields that should be defined in OCaml but
+  skipped during serialization/deserialization
+
+
+Piqi-ocaml 0.7.5 (May 31, 2016)
+===============================
+
+- Switch to tail-recursive List.map in the piqirun.ml runtime library
+- (new feature) Support for overriding ocaml name of an imported module
+
+
+Piqi-ocaml 0.7.4 (Mar 13, 2015)
+===============================
+
+- Fix build and tests for OCaml < 4.02.0
+
+
+Piqi-ocaml 0.7.3 (Mar 13, 2015)
+===============================
+
+- Fix compilation warnings for OCaml >= 4.02
+
+
+Piqi-ocaml 0.7.2 (May 17, 2014)
+===============================
+
+New features:
+
+  - Automatically prefix OCaml keywords and user-specified reserved names with
+    underscores in generated OCaml code (thanks to Petter Urkedal)
+
+
+Piqi-ocaml 0.7.1 (April 17, 2014)
+=================================
+
+Fixes:
+
+  - 'piqic-ocaml --normalize-names' should be true by default
+
+Other changes:
+
+  - piqic-ocaml: indent generated .ml code instead of relying on camlp4o
+
+
+Piqi-ocaml 0.7.0 (April 7, 2014)
+================================
+
+The main change of this release is the rewrite of the "piqic-ocaml" code
+generator on top of "piqi compile" interfaces. As a result, we were able to move
+the piqi-ocaml code from the main Piqi project repository into its own
+piqi-ocaml repo.
+
+Other important changes:
+
+  - "piqic ocaml" becomes "piqic-ocaml"
+  - "piqic ocaml-ext" turns into "piqic-ocaml --ext"
+  - "piqirun" becomes a package with two subpackages: piqirun.pb -- for Protobuf
+    serialization and piqirun.ext -- for multi-format serialization; piqirun.pb
+    should be now used instead of piqirun package and piqirun.ext -- instead of
+    piqi.lib
+  - "--gen-defaults" compiler option is deprecated. "piqic-ocaml" now generates
+    _piqi.default_X automatically
+  - Much more cleaner and stable interfaces in the piqilib dependency (those
+    that piqi-ocaml depends on); this allows us to release piqilib and
+    piqi-ocaml independently
+  - Drop support for OCaml <= 3.11
+  - Deprecate and remove "pa_openin" camlp4 extension; "pa_labelscope"
+    extensions is kept for now as a part of the piqilib package so that existing
+    programs can still use it
+  - Deprecate and remove "piqic-ocaml -o <ofile>" command-line option
+
+Fixes:
+
+  - Fix generation of incorrect code for custom OCaml types
+
+New features:
+
+  - Preserve unknown Protobuf fields through deserialization-serialization cycle
+    (new piqic-ocaml --gen-preserve-unknown-fields flag)
+  - New conversion options: piq_frameless_output, piq_frameless_input,
+    piq_relaxed_parsing
+  - Add the ability to specify conversion options for generated
+    _piqi_ext.print_/prerr_ functions
+  - Add piqic-ocaml --piqi-version flag for printing piqilib version
+  - Add piqic-ocaml --runtime <module> option for specifying the name of the
+    Protobuf serialization runtime module (default = Piqirun)
+
+Miscellaneous:
+
+  - Rename conversion option: json_omit_null_fields -> json_omit_missing_fields
+  - Improved piqi-ocaml documentation (available at doc/piqi-ocaml.md)
+  - Continuous builds via Travis-CI
+
+
+Piqi 0.6.5 (October 27, 2013)
+=============================
+
+  Changelog for v0.6.5 and earlier releases is available here (the piqi-ocaml
+  project used to be a subtree in the piqi repository):
+
+      https://github.com/alavrik/piqi/blob/master/CHANGES
+

piqi-ocaml/LICENSE

@@ -0,0 +1,178 @@
+
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piqi-ocaml/Makefile

@@ -0,0 +1,31 @@
+include make/Makefile.dirs
+
+
+DESTDIR ?= /usr/local
+
+
+DIRS = piqirun piqic-ocaml
+
+
+.PHONY: install uninstall clean distclean test
+
+
+install:
+	$(MAKE) -C piqirun install
+	-install -d $(DESTDIR)/bin
+	install piqic-ocaml/piqic-ocaml $(DESTDIR)/bin
+
+
+uninstall:
+	$(MAKE) -C piqirun uninstall
+	rm -f $(DESTDIR)/bin/piqic-ocaml
+
+
+test:
+	$(MAKE) -C tests
+
+
+distclean:
+	$(MAKE) clean
+	$(MAKE) -C tests clean
+