bug#19237: Guile-2.0.11 OS X 10.10.1 build error

[Hans Aberg]

I get a build error [1] with guile-2.0.11 on OS X 10.10.1. It looks like an 
illegal int to pointer conversion cause a name to not be defined, and then the 
linking fails.


1. make
...
Making all in guile-readline
  SNARF  readline.x
/Applications/Xcode.app/Contents/Developer/usr/bin/make  all-am
  CC       readline.lo
../../guile-2.0.11/guile-readline/readline.c:433:16: warning: implicit 
declaration of function 'rl_get_keymap_name' is invalid in C99
      [-Wimplicit-function-declaration]
  if (strncmp (rl_get_keymap_name (rl_get_keymap ()), "vi", 2))
               ^
../../guile-2.0.11/guile-readline/readline.c:433:16: warning: incompatible 
integer to pointer conversion passing 'int' to parameter of type 'const char *'
      [-Wint-conversion]
  if (strncmp (rl_get_keymap_name (rl_get_keymap ()), "vi", 2))
               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/string.h:84:26: note: passing argument to parameter here
int      strncmp(const char *, const char *, size_t);
                             ^
2 warnings generated.
  CCLD     libguilereadline-v-18.la
Undefined symbols for architecture x86_64:
  "_rl_get_keymap_name", referenced from:
      _scm_init_readline in readline.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[3]: *** [libguilereadline-v-18.la] Error 1
make[2]: *** [all] Error 2
make[1]: *** [all-recursive] Error 1
make: *** [all] Error 2