Various changes:

Updated top CMakeFile.txt
Moved volk module to a better path.
Trying to add support for GCC.
Fixes.

src/algorithms/libs/volk_gnsssdr_module/CMakeLists.txt

@@ -0,0 +1,50 @@
+# Copyright (C) 2012-2014  (see AUTHORS file for a list of contributors)
+#
+# This file is part of GNSS-SDR.
+#
+# GNSS-SDR is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# GNSS-SDR is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with GNSS-SDR. If not, see <http://www.gnu.org/licenses/>.
+#
+
+###############################################################################
+# Volk_gnsssdr module
+#In order to use volk_gnsssr module it is necessary to add:
+# 1) include_directories(..${VOLK_GNSSSDR_INCLUDE_DIRS}..)
+# 2) target_link_libraries(..${VOLK_GNSSSDR_LIBRARIES}..)
+###############################################################################
+
+message(STATUS " START OF: Setup volk_gnsssdr as a subproject.")
+
+set(VOLK_GNSSSDR_BASE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/volk_gnsssdr)
+
+set(CMAKE_INSTALL_PREFIX ${CMAKE_CURRENT_BINARY_DIR}/volk_gnsssdr/lib)
+list(APPEND CMAKE_C_FLAGS "-std=c11")
+
+add_subdirectory(${VOLK_GNSSSDR_BASE_PATH})
+
+set(VOLK_GNSSSDR_INCLUDE_DIRS
+     ${VOLK_GNSSSDR_BASE_PATH}/include
+     ${CMAKE_CURRENT_BINARY_DIR}/volk_gnsssdr/include
+     CACHE INTERNAL ""
+)
+
+set(VOLK_GNSSSDR_LIBRARIES
+     #Path to libs of volk_gnsssdr target: ${VOLK_GNSSSDR_BASE_PATH}/lib/Debug/libvolk_gnsssdr.dylib
+     volk_gnsssdr
+     CACHE INTERNAL ""
+)
+
+message(STATUS " * INCLUDES: ${VOLK_GNSSSDR_INCLUDE_DIRS} ")
+message(STATUS " * LIBS: ${VOLK_GNSSSDR_LIBRARIES} ")
+message(STATUS " END OF: Setup volk_gnsssdr as a subproject.")
+