patch 8.0.0464: can't find executable name on Solaris and FreeBSD

Problem:    Can't find executable name on Solaris and FreeBSD.
Solution:   Check for "/proc/self/path/a.out". (Danek Duvall) And for
            "/proc/curproc/file".
diff --git a/src/auto/configure b/src/auto/configure
index 73b9ce7..44532cf 100755
--- a/src/auto/configure
+++ b/src/auto/configure
@@ -10101,15 +10101,25 @@
 
 
 
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for /proc/self/exe" >&5
-$as_echo_n "checking for /proc/self/exe... " >&6; }
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for /proc link to executable" >&5
+$as_echo_n "checking for /proc link to executable... " >&6; }
 if test -L "/proc/self/exe"; then
-    { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
-$as_echo "yes" >&6; }
-    $as_echo "#define HAVE_PROC_SELF_EXE 1" >>confdefs.h
+    { $as_echo "$as_me:${as_lineno-$LINENO}: result: /proc/self/exe" >&5
+$as_echo "/proc/self/exe" >&6; }
+  $as_echo "#define PROC_EXE_LINK \"/proc/self/exe\"" >>confdefs.h
+
+elif test -L "/proc/self/path/a.out"; then
+    { $as_echo "$as_me:${as_lineno-$LINENO}: result: /proc/self/path/a.out" >&5
+$as_echo "/proc/self/path/a.out" >&6; }
+  $as_echo "#define PROC_EXE_LINK \"/proc/self/path/a.out\"" >>confdefs.h
+
+elif test -L "/proc/curproc/file"; then
+    { $as_echo "$as_me:${as_lineno-$LINENO}: result: /proc/curproc/file" >&5
+$as_echo "/proc/curproc/file" >&6; }
+  $as_echo "#define PROC_EXE_LINK \"/proc/curproc/file\"" >>confdefs.h
 
 else
-    { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
 $as_echo "no" >&6; }
 fi
 
diff --git a/src/config.h.in b/src/config.h.in
index a9bcf1e..f8a23ed 100644
--- a/src/config.h.in
+++ b/src/config.h.in
@@ -446,8 +446,8 @@
 /* Define if fcntl()'s F_SETFD command knows about FD_CLOEXEC */
 #undef HAVE_FD_CLOEXEC
 
-/* Define if /proc/self/exe can be read */
-#undef HAVE_PROC_SELF_EXE
+/* Define if /proc/self/exe or similar can be read */
+#undef PROC_EXE_LINK
 
 /* Define if you want Cygwin to use the WIN32 clipboard, not compatible with X11*/
 #undef FEAT_CYGWIN_WIN32_CLIPBOARD
diff --git a/src/configure.ac b/src/configure.ac
index 4445cf5..6251681 100644
--- a/src/configure.ac
+++ b/src/configure.ac
@@ -3020,12 +3020,21 @@
 dnl end of GUI-checking
 dnl ---------------------------------------------------------------------------
 
-AC_MSG_CHECKING([for /proc/self/exe])
+AC_MSG_CHECKING([for /proc link to executable])
 if test -L "/proc/self/exe"; then
-    AC_MSG_RESULT(yes)
-    AC_DEFINE(HAVE_PROC_SELF_EXE)
+  dnl Linux
+  AC_MSG_RESULT([/proc/self/exe])
+  AC_DEFINE(PROC_EXE_LINK, "/proc/self/exe")
+elif test -L "/proc/self/path/a.out"; then
+  dnl Solaris
+  AC_MSG_RESULT([/proc/self/path/a.out])
+  AC_DEFINE(PROC_EXE_LINK, "/proc/self/path/a.out")
+elif test -L "/proc/curproc/file"; then
+  dnl FreeBSD
+  AC_MSG_RESULT([/proc/curproc/file])
+  AC_DEFINE(PROC_EXE_LINK, "/proc/curproc/file")
 else
-    AC_MSG_RESULT(no)
+  AC_MSG_RESULT(no)
 fi
 
 dnl Check for Cygwin, which needs an extra source file if not using X11
diff --git a/src/main.c b/src/main.c
index aa5a1a2..29ab3c6 100644
--- a/src/main.c
+++ b/src/main.c
@@ -3539,11 +3539,11 @@
 {
     char_u *val = argv0;
 
-# ifdef HAVE_PROC_SELF_EXE
+# ifdef PROC_EXE_LINK
     char    buf[PATH_MAX + 1];
     ssize_t len;
 
-    len = readlink("/proc/self/exe", buf, PATH_MAX);
+    len = readlink(PROC_EXE_LINK, buf, PATH_MAX);
     if (len > 0)
     {
 	buf[len] = NUL;
diff --git a/src/version.c b/src/version.c
index c1ac29d..efef5f8 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    464,
+/**/
     463,
 /**/
     462,