set compiler standard to ISO C90/ANSI C89 (#577)

SonarCloud is outputting some code smells for things that aren't possible for C89. Hopefully setting the code standard to C89/C90 properly will fix those bogus warnings.

Fix By: Brad House (@bradh352)

src/lib/CMakeLists.txt

@@ -34,6 +34,7 @@ IF (CARES_SHARED)
 		COMPILE_PDB_OUTPUT_DIRECTORY ${CMAKE_RUNTIME_OUTPUT_DIRECTORY}
 		SOVERSION                    ${CARES_LIB_VERSION_MAJOR}
 		VERSION                      "${CARES_LIB_VERSION_MAJOR}.${CARES_LIB_VERSION_MINOR}.${CARES_LIB_VERSION_RELEASE}"
+		C_STANDARD                   90
 	)
 
 	TARGET_INCLUDE_DIRECTORIES (${PROJECT_NAME}
@@ -78,6 +79,7 @@ IF (CARES_STATIC)
 		OUTPUT_NAME                  cares${STATIC_SUFFIX}
 		COMPILE_PDB_NAME             cares${STATIC_SUFFIX}
 		COMPILE_PDB_OUTPUT_DIRECTORY ${CMAKE_RUNTIME_OUTPUT_DIRECTORY}
+		C_STANDARD                   90
 	)
 
 	IF (CARES_STATIC_PIC)

src/tools/CMakeLists.txt

@@ -15,6 +15,9 @@ IF (CARES_BUILD_TOOLS)
 		       "$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>"
 		PRIVATE "${CMAKE_CURRENT_SOURCE_DIR}"
 	)
+	SET_TARGET_PROPERTIES (ahost PROPERTIES
+		C_STANDARD                   90
+	)
 	TARGET_COMPILE_DEFINITIONS (ahost PRIVATE HAVE_CONFIG_H=1)
 	TARGET_LINK_LIBRARIES (ahost PRIVATE ${PROJECT_NAME})
 	IF (CARES_INSTALL)
@@ -32,6 +35,9 @@ IF (CARES_BUILD_TOOLS)
 		       "$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>"
 		PRIVATE "${CMAKE_CURRENT_SOURCE_DIR}"
 	)
+	SET_TARGET_PROPERTIES (adig PROPERTIES
+		C_STANDARD                   90
+	)
 	TARGET_COMPILE_DEFINITIONS (adig PRIVATE HAVE_CONFIG_H=1)
 	TARGET_LINK_LIBRARIES (adig PRIVATE ${PROJECT_NAME})
 	IF (CARES_INSTALL)