Make checks for headers and libraries actually halt configure.

configure.ac

@@ -2,7 +2,7 @@
 # Process this file with autoconf to produce a configure script.
 
 AC_PREREQ(2.57)
-AC_INIT([htop],[0.6.2],[loderunner@users.sourceforge.net])
+AC_INIT([htop],[0.6.3],[loderunner@users.sourceforge.net])
 AM_INIT_AUTOMAKE
 AC_CONFIG_SRCDIR([htop.c])
 AC_CONFIG_HEADER([config.h])
@@ -11,13 +11,23 @@ AC_CONFIG_HEADER([config.h])
 AC_PROG_CC
 
 # Checks for libraries.
-AC_CHECK_LIB([ncurses], [refresh])
-AC_CHECK_LIB([m], [ceil])
+AC_CHECK_LIB([ncurses], [refresh], [], [missing_libraries="$missing_libraries libncurses"])
+AC_CHECK_LIB([m], [ceil], [], [missing_libraries="$missing_libraries libm"])
+
+if test ! -z "$missing_libraries"; then
+  AC_MSG_ERROR([missing libraries:$missing_headers])
+fi
 
 # Checks for header files.
 AC_HEADER_DIRENT
 AC_HEADER_STDC
-AC_CHECK_HEADERS([stdlib.h string.h strings.h sys/param.h sys/time.h unistd.h curses.h])
+AC_CHECK_HEADERS([stdlib.h string.h strings.h sys/param.h sys/time.h unistd.h curses.h],[:],[
+  missing_headers="$missing_headers $ac_header"
+])
+
+if test ! -z "$missing_headers"; then
+  AC_MSG_ERROR([missing headers:$missing_headers])
+fi
 
 # Checks for typedefs, structures, and compiler characteristics.
 AC_HEADER_STDBOOL