initial stab at finding mysql headers easier

ext/extconf.rb

@@ -1,9 +1,11 @@
 # encoding: UTF-8
-
 require 'mkmf'
+
 dir_config('mysql')
 
-have_header('mysql/mysql.h')
+if !have_header('mysql.h') && !have_header('mysql/mysql.h')
+  raise 'MySQL headers not found, maybe try manually specifying --with-mysql=/path/to/mysql/installation'
+end
 
 $CFLAGS << ' -Wall -Wextra -funroll-loops'
 # $CFLAGS << ' -O0 -ggdb3'
@@ -15,5 +17,5 @@ if have_library('mysqlclient')
 
   create_makefile('mysql2_ext')
 else
-  puts 'libmysql not found, maybe try manually specifying --with-mysql-lib to find it?'
+  raise 'libmysql not found, maybe try manually specifying --with-mysql-lib=/path/to/mysql/libs'
 end