libcall: remove libcall ifdefs

Remove all the legacy code that related to mch_libcall in some way.
os_libcall is implemented on top of libuv now.

src/nvim/eval.c

@@ -9674,9 +9674,7 @@ static void f_has(typval_T *argvars, typval_T *rettv)
     "jumplist",
     "keymap",
     "langmap",
-#ifdef FEAT_LIBCALL
     "libcall",
-#endif
     "linebreak",
     "lispindent",
     "listcmds",

src/nvim/globals.h

@@ -1006,9 +1006,7 @@ EXTERN char_u e_isadir2[] INIT(= N_("E17: \"%s\" is a directory"));
 EXTERN char_u e_invjob[] INIT(= N_("E900: Invalid job id"));
 EXTERN char_u e_jobtblfull[] INIT(= N_("E901: Job table is full"));
 EXTERN char_u e_jobexe[] INIT(= N_("E902: \"%s\" is not an executable"));
-#ifdef FEAT_LIBCALL
 EXTERN char_u e_libcall[] INIT(= N_("E364: Library call failed for \"%s()\""));
-#endif
 EXTERN char_u e_markinval[] INIT(= N_("E19: Mark has invalid line number"));
 EXTERN char_u e_marknotset[] INIT(= N_("E20: Mark not set"));
 EXTERN char_u e_modifiable[] INIT(= N_(

src/nvim/os_unix.c

@@ -70,11 +70,6 @@
 # include <termios.h>
 #endif
 
-/* shared library access */
-#if defined(HAVE_DLFCN_H) && defined(USE_DLOPEN)
-# include <dlfcn.h>
-#endif
-
 #ifdef HAVE_SELINUX
 # include <selinux/selinux.h>
 static int selinux_enabled = -1;

src/nvim/version.c

@@ -98,11 +98,7 @@ static char *(features[]) = {
   "+jumplist",
   "+keymap",
   "+langmap",
-#ifdef FEAT_LIBCALL
   "+libcall",
-#else   // ifdef FEAT_LIBCALL
-  "-libcall",
-#endif  // ifdef FEAT_LIBCALL
   "+linebreak",
   "+lispindent",
   "+listcmds",