Add GNU make based build system

Add a single makefile such that it will rarely need modifications
with regular source code changes.

The usual configure step for build environment detection is done
manually by editing config.mk, it is expected to be simple make
variable changes (mostly CFLAGS), later a simple configure script
can be added to generate config.mk if necessary.

Update the README.
diff --git a/README b/README
index 5b5fbc1..c5de9bf 100644
--- a/README
+++ b/README
@@ -1,73 +1,43 @@
-ARM math library functions
-----------------------------
+Arm Optimized Routines
+----------------------
 
-This package contains a number of math functions from ARM's math library,
-as well as a build system and a test suite. In addition to the source code,
-there is also a script "remez.jl", which was used to generate coefficients
-used in the implementation of these functions (see comments in the code).
+This repository contains implementations of math library functions
+provided by Arm under Apache License 2.0 (See LICENSE). Contributions
+to this project are accepted, but the terms will need negotiation (so
+relicensing and copyright assignment to the FSF is possible later).
 
-Requirements: gcc >= 4.8, cmake >= 2.8, mpfr, mpc, qemu-user-static.
+Source code layout:
 
-For a native build on an AArch64 platform, everything (including tests) should
-work out-of the box, assuming the system compiler is a recent gcc. Simply follow
-the instructions below to configure the build using cmake (leaving out the
--DCMAKE_TOOLCHAIN_FILE argument).
+auxiliary/      - design tools.
+build/          - build directory (created by make).
+math/           - math library source.
+math/include/   - math library public headers.
+math/single/    - code for cpu with only single precision support.
+test/           - test related source.
+test/rtest/     - test generator (requires mpfr and mpc).
+test/testcases/ - test cases.
 
-Cross builds are supported for Linux hosts. First, install the required
-packages to build and run the tests on your distro of choice:
-# apt-get install qemu-user-static gcc-aarch64-linux-gnu libmpfr-dev \
-  libmpc-dev cmake
+The steps to build the library and run the tests:
 
-You could also use a custom aarch64-linux-gnu-gcc cross toolchain, e.g. from
-Linaro, if your system doesn't provide one:
-
-https://releases.linaro.org/15.02/components/toolchain/binaries/
-
-The build script will build both a shared and a static math library object
-containing the ARM functions for the specified target, a host-side application
-rtest that generates test cases, and a target-side application mathtest that is
-linked against the math library and actually executes the tests.
-
-Generally, the steps to build and run the tests are:
-
-mkdir -p /my/build/folder && cd /my/build/folder
-cmake /path/to/src -DCMAKE_TOOLCHAIN_FILE=/path/to/toolchain/file
+cp config.mk.dist config.mk
+# edit config.mk if necessary ...
 make
 make check
 
-The toolchain file specifies the paths to the cross-compiler, i.e.
-aarch64-linux-gnu-gcc, as well as the sysroot parameter for the build. An
-example can be found in toolchain-gcc.cmake, which assumes that you have
-the cross toolchain installed in /usr/bin and the sysroot is
-/usr/aarch64-linux-gnu respectively. This should work with the Ubuntu packages
-suggested above as-is. Edit the paths as necessary if your cross toolchain
-lives somewhere else. Alternatively, you can specify the necessary parameters
-from the toolchain file directly on the command line.
+Or building outside of the source directory:
 
-The files are built in the build directory as follows:
-build/
-  bin/
-    rtest
-    mathtest
-    runtest.sh
-  lib/
-    libmathlib.so
-    libmathlib_static.a
-  include/
-    arm_math.h
+ln -s path/to/src/Makefile Makefile
+cp path/to/src/config.mk.dist config.mk
+echo 'srcdir = path/to/src' >> config.mk
+# further edits to config.mk
+make
+make check
 
-It is possible to specify which emulator to use for the execution of the tests
-in the cross compilation case by specifying the following option:
-cmake (...) -DCMAKE_CROSSCOMPILING_EMULATOR=/path/to/your/emulator
-By default, qemu-aarch64-static will be used, so this has to be on your path
-if you want to cross-run the test suite.
+The test system requires libmpfr and libmpc.
 
-Whenever the CMake configuration is changed, it is wise to delete the whole
-build folder instead of just rerunning CMake inside the existing folder.
+For cross build, CROSS_COMPILE should be set in config.mk and EMULATOR
+should be set for cross testing (e.g. using qemu-user or remote access
+to a target machine), see the examples in config.mk.dist.
 
-The build system also has experimental support for using clang as the cross
-compiler.
-!!!You need CMake >= 3.0 and clang >= 3.5.0 for this!!!
-Before compilation, apply the source patch in the patches/ folder to make sure
-everything works properly when compiled with clang. There is a sample toolchain
-file for clang included as toolchain-clang.cmake.
+The script "remez.jl" was used to generate some of the coefficients
+(see comments in the code).