Move readline to the readline/readline subdirectory

readline turns out to be a bit of a stumbling block for the project to
move gdbsupport (and then gdbserver) to the top-level.

The issue is that readline headers are intended to be included with
names like "readline/readline.h".  To support this, gdb effectively
adds a -I option pointing to the top-level source directory -- but,
importantly, this option is not used when the system readline is used.

For gdbsupport, a -I option like this would always be needed, but that
in turn would break the system readline case.  This was PR build/17077,
fixed in commit a8a5dbcab8df0b3a9e04745d4fe8d64740acb323.

Previously, we had discussed this on the gdb-patches list in terms of
removing readline from the tree

    https://sourceware.org/ml/gdb-patches/2019-09/msg00317.html

However, Eli expressed some concerns, and Joel did as well (off-list).

Given those concerns, and the fact that a patch-free local readline is
relatively new in gdb (it was locally patched for years), I changed my
mind and decided to handle this situation by moving the readline
sources down a level.

That is, upstream readline is now in readline/readline, and the
top-level readline directory just contains the minimal configury
needed to build that.

This fixes the problem because, when gdb unconditionally adds a
-I$(top_srcdir), this will not find readline headers.  A separate -I
will be needed instead, which is exactly what's needed for
--with-system-readline.

gdb/ChangeLog
2019-10-23  Tom Tromey  <tom@tromey.com>

	* Makefile.in (READLINE_DIR): Update.

gdb/doc/ChangeLog
2019-10-23  Tom Tromey  <tom@tromey.com>

	* Makefile.in (READLINE_DIR): Update.

readline/ChangeLog
2019-10-23  Tom Tromey  <tom@tromey.com>

	Move old contents to readline/ subdirectory.
	* aclocal.m4, configure, configure.ac, .gitignore, Makefile.am,
	Makefile.in, README: New files.

Change-Id: Ice156a2ee09ea68722b48f64d97146d7428ea9e4

4 files changed, 11 insertions, 3 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index a976d8f..7dd596e 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,7 @@
+2019-10-23  Tom Tromey  <tom@tromey.com>
+
+	* Makefile.in (READLINE_DIR): Update.
+
 2019-10-23  Tankut Baris Aktemur  <tankut.baris.aktemur@intel.com>
 
 	* infcall.c (call_function_by_hand_dummy): Fix the function
diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index 553b3ff..fe599b4 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -174,8 +174,8 @@ LIBDECNUMBER = $(LIBDECNUMBER_DIR)/libdecnumber.a
 LIBDECNUMBER_SRC = $(srcdir)/$(LIBDECNUMBER_DIR)
 LIBDECNUMBER_CFLAGS = -I$(LIBDECNUMBER_DIR) -I$(LIBDECNUMBER_SRC)
 
-# Where is the READLINE library?  Typically in ../readline.
-READLINE_DIR = ../readline
+# Where is the READLINE library?  Typically in ../readline/readline.
+READLINE_DIR = ../readline/readline
 READLINE_SRC = $(srcdir)/$(READLINE_DIR)
 READLINE = @READLINE@
 READLINE_DEPS = @READLINE_DEPS@
diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index b81c2cc..0d0d905 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,3 +1,7 @@
+2019-10-23  Tom Tromey  <tom@tromey.com>
+
+	* Makefile.in (READLINE_DIR): Update.
+
 2019-10-23  Christian Biesinger  <cbiesinger@google.com>
 
 	* python.texi (Threads In Python): Add a note for how to get the
diff --git a/gdb/doc/Makefile.in b/gdb/doc/Makefile.in
index 2bb8a30..2673499 100644
--- a/gdb/doc/Makefile.in
+++ b/gdb/doc/Makefile.in
@@ -74,7 +74,7 @@ BUGURL_TEXI = @REPORT_BUGS_TEXI@
 
 # Where is the source dir for the READLINE library doc?  
 # Traditionally readline is in .. or .
-READLINE_DIR = ${gdbdir}/../readline/doc
+READLINE_DIR = ${gdbdir}/../readline/readline/doc
 READLINE_TEXI_INCFLAG = @READLINE_TEXI_INCFLAG@
 
 # The GDB/MI docs come from a sibling directory ../mi