Rename Py_BUILD_ASSERT to Py_BUILD_ASSERT_EXPR

To make it clearer that Py_BUILD_ASSERT_EXPR(cond) cannot be used as
assert(cond).

Include/pymacro.h

@@ -17,18 +17,17 @@
 
    #define foo_to_char(foo)  \
        ((char *)(foo)        \
-        + Py_BUILD_ASSERT(offsetof(struct foo, string) == 0))
+        + Py_BUILD_ASSERT_EXPR(offsetof(struct foo, string) == 0))
 
    Written by Rusty Russell, public domain, http://ccodearchive.net/ */
-#define Py_BUILD_ASSERT(cond) \
+#define Py_BUILD_ASSERT_EXPR(cond) \
     (sizeof(char [1 - 2*!(cond)]) - 1)
 
-
 /* Get the number of elements in a visible array
 
    This does not work on pointers, or arrays declared as [], or function
    parameters. With correct compiler support, such usage will cause a build
-   error (see Py_BUILD_ASSERT).
+   error (see Py_BUILD_ASSERT_EXPR).
 
    Written by Rusty Russell, public domain, http://ccodearchive.net/ */
 #if defined(__GNUC__)
@@ -36,7 +35,7 @@
    &a[0] degrades to a pointer: a different type from an array */
 #define Py_ARRAY_LENGTH(array) \
     (sizeof(array) / sizeof((array)[0]) \
-     + Py_BUILD_ASSERT(!__builtin_types_compatible_p(typeof(array), \
+     + Py_BUILD_ASSERT_EXPR(!__builtin_types_compatible_p(typeof(array), \
                                                           typeof(&(array)[0]))))
 #else
 #define Py_ARRAY_LENGTH(array) \