C: change phone-number to exercism V3

c/phone-number/br-common.h

@@ -0,0 +1,45 @@
+#ifndef __BR_COMMON_H
+#define __BR_COMMON_H
+
+/* ${LINUX_SRC}/include/linux/compiler_attributes.h, around line 30
+ *
+ * __has_attribute is supported on gcc >= 5, clang >= 2.9 and icc >= 17.
+ * For other compilers, simple implementation (for __falltrough__ only)
+ */
+#ifndef __has_attribute
+#  define __has_attribute(x) __GCC4_has_attribute_##x
+#  define __GCC4_has_attribute___assume_aligned__      (__GNUC_MINOR__ >= 9)
+#  define __GCC4_has_attribute___copy__                0
+#  define __GCC4_has_attribute___designated_init__     0
+#  define __GCC4_has_attribute___externally_visible__  1
+#  define __GCC4_has_attribute___no_caller_saved_registers__ 0
+#  define __GCC4_has_attribute___noclone__             1
+#  define __GCC4_has_attribute___nonstring__           0
+#  define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
+#  define __GCC4_has_attribute___no_sanitize_undefined__ (__GNUC_MINOR__ >= 9)
+#  define __GCC4_has_attribute___fallthrough__         0
+#  define __GCC4_has_attribute___fallthrough__         0
+#endif
+
+/* ${LINUX_SRC}/include/linux/compiler_attributes.h, around line 200
+ */
+#if __has_attribute(__fallthrough__)
+#  define fallthrough                    __attribute__((__fallthrough__))
+#else
+#  define fallthrough                    do {} while (0);  /* fallthrough */
+#endif
+
+/* See GNUmakefile below for explanation
+ * https://github.com/braoult/exercism/blob/master/c/templates/GNUmakefile
+ */
+#if defined UNIT_TEST || defined DEBUG
+#  include <stdio.h>
+#  include <stdlib.h>
+#endif
+
+#ifdef  TESTALL
+#  undef  TEST_IGNORE
+#  define TEST_IGNORE() {}
+#endif
+
+#endif  /* __BR_COMMON_H */