Remove submodules in order to be included as subtrees

See https://github.com/apenwarr/git-subtree

diff --git a/src/fna b/src/fna
deleted file mode 160000 (submodule)
index 493e9e8..0000000
--- a/src/fna
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit 493e9e8be9c3761691b96e8366d036d6b3c314fb

diff --git a/src/forb b/src/forb
deleted file mode 160000 (submodule)
index 1ef7503..0000000
--- a/src/forb
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit 1ef7503676513a85e80eda0950d0cae8b60d7cdd

diff --git a/src/fosa b/src/fosa
deleted file mode 160000 (submodule)
index 74de0ef..0000000
--- a/src/fosa
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit 74de0ef982fc4f9a7e6587e45367a8819d4efe7f

diff --git a/src/frsh b/src/frsh
deleted file mode 160000 (submodule)
index 3d8b226..0000000
--- a/src/frsh
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit 3d8b226fce42630a1d0ee32917f0ab54fcfc30ee

diff --git a/src/frsh-include b/src/frsh-include
deleted file mode 160000 (submodule)
index 2ca79f7..0000000
--- a/src/frsh-include
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit 2ca79f782952a3d871591bfce458b88d9d359c9a

diff --git a/src/fwp b/src/fwp
deleted file mode 160000 (submodule)
index 898e542..0000000
--- a/src/fwp
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit 898e54279f22559dd6acd2b7061bb36e8cb0975e

diff --git a/src/ulut b/src/ulut
deleted file mode 160000 (submodule)
index ba97076..0000000
--- a/src/ulut
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit ba970760b38b93d1a3f163c0c5b5c790024372dd

diff --git a/src/wvtest b/src/wvtest
deleted file mode 160000 (submodule)
index f428a8b..0000000
--- a/src/wvtest
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit f428a8b07c5badb5e27749c9d6b4ba4585b5d5ee