Modularize code: main.c -> device-cpu + device-gpu

This patch is an initial attempt to re-structure cgminer source
code from its monolithic design (with nearly all code being
concentrated in main.c) to a more modular one.

In this first stage, the conditionally compiled functions for
GPU and CPU mining were extracted into dedicated files:
 * device-cpu.h and device-cpu.c covering WANT_CPUMINE functions
 * device-gpu.h and device-gpu.c covering HAVE_OPENCL functions

The main.c file is left untouched as reference, while the
remainder without the extracted parts is located in cgminer.c.

The Makefile.am has been updated to use the re-structured
source files for the build.

Above pure re-structuring *NO* functional modifications were
made. The sources were tested to compile and run on on a
current Linux system with working CPU and GPU mining
(Bitforce not tested due to loack of hardware).

Makefile.am

@@ -17,50 +17,59 @@ INCLUDES	= $(PTHREAD_FLAGS) -fno-strict-aliasing $(JANSSON_INCLUDES)
 
 bin_PROGRAMS	= cgminer
 
-bin_SCRIPTS	= phatk110817.cl poclbm110817.cl
-
-if HAS_CPUMINE
-cgminer_SOURCES	= elist.h miner.h compat.h bench_block.h	\
-		  main.c util.c uthash.h			\
-		  ocl.c ocl.h findnonce.c findnonce.h 		\
-		  sha256_generic.c sha256_4way.c sha256_via.c	\
-		  sha256_cryptopp.c sha256_sse2_amd64.c		\
-		  sha256_sse4_amd64.c sha256_sse2_i386.c	\
-		  sha256_altivec_4way.c				\
-		  adl.c	adl.h adl_functions.h			\
-		  phatk110817.cl poclbm110817.cl \
-		  sha2.c sha2.h api.c
-else
-cgminer_SOURCES	= elist.h miner.h compat.h bench_block.h	\
-		  main.c util.c uthash.h			\
-		  ocl.c ocl.h findnonce.c findnonce.h 		\
-		  adl.c	adl.h adl_functions.h			\
-		  phatk110817.cl poclbm110817.cl \
-		  sha2.c sha2.h api.c
-endif
+bin_SCRIPTS	= phatk120203.cl poclbm120203.cl
 
 cgminer_LDFLAGS	= $(PTHREAD_FLAGS)
 cgminer_LDADD	= $(DLOPEN_FLAGS) @LIBCURL_LIBS@ @JANSSON_LIBS@ @PTHREAD_LIBS@ \
 		  @OPENCL_LIBS@ @NCURSES_LIBS@ @PDCURSES_LIBS@ @WS2_LIBS@ \
 		  @MATH_LIBS@ lib/libgnu.a ccan/libccan.a
 cgminer_CPPFLAGS = -I$(top_builddir)/lib -I$(top_srcdir)/lib @OPENCL_FLAGS@
 
+# common sources
+
+# this is the original monolithic main.c, kept as reference
+# cgminer_SOURCES	:= main.c
+
+# this is the original main.c without extracted CPU and GPU code
+cgminer_SOURCES := cgminer.c
+
+cgminer_SOURCES	+= elist.h miner.h compat.h bench_block.h	\
+		   util.c uthash.h				\
+		   sha2.c sha2.h api.c
+
+# GPU sources, TODO: make them selectable
+# the GPU portion extracted from original main.c
+cgminer_SOURCES += device-gpu.h device-gpu.c
+
+# the original GPU related sources, unchanged
+cgminer_SOURCES += ocl.c ocl.h findnonce.c findnonce.h
+cgminer_SOURCES += adl.c adl.h adl_functions.h
+cgminer_SOURCES += phatk120203.cl poclbm120203.cl
+
 if HAS_CPUMINE
-if HAVE_x86_64
+# original CPU related sources, unchanged
+cgminer_SOURCES	+= \
+		  sha256_generic.c sha256_4way.c sha256_via.c	\
+		  sha256_cryptopp.c sha256_sse2_amd64.c		\
+		  sha256_sse4_amd64.c sha256_sse2_i386.c	\
+		  sha256_altivec_4way.c
+
+# the CPU portion extracted from original main.c
+cgminer_SOURCES += device-cpu.h device-cpu.c
+
 if HAS_YASM
+AM_CFLAGS	= -DHAS_YASM
+if HAVE_x86_64
 SUBDIRS		+= x86_64
 cgminer_LDADD	+= x86_64/libx8664.a
-AM_CFLAGS	= -DHAS_YASM
-endif
-else
-if HAS_YASM
+else # HAVE_x86_64
 SUBDIRS		+= x86_32
 cgminer_LDADD	+= x86_32/libx8632.a
-AM_CFLAGS	= -DHAS_YASM
-endif
-endif
-endif
+endif # HAVE_x86_64
+endif # HAS_YASM
+endif # HAS_CPUMINE
 
 if HAS_BITFORCE
 cgminer_SOURCES += bitforce.c
 endif
+