Fix some typos (#1378)

Author: fkmy

README.md

@@ -133,7 +133,7 @@ $ bundle config --local build.mysql2 -- $(ruby -r rbconfig -e 'puts RbConfig::CO
 ```
 
 Note the additional double dashes (`--`) these separate command-line arguments
-that `gem` or `bundler` interpret from the addiitonal arguments that are passed
+that `gem` or `bundler` interpret from the additional arguments that are passed
 to the mysql2 build process.
 
 ### Windows

ext/mysql2/client.c

@@ -307,7 +307,7 @@ static void *nogvl_connect(void *ptr) {
  * a socket that may be in use by the parent or other processes after fork.
  *
  * /dev/null is used to absorb writes; previously a dummy socket was used, but
- * it could not abosrb writes and caused openssl to go into an infinite loop.
+ * it could not absorb writes and caused openssl to go into an infinite loop.
  *
  * Returns Qtrue or Qfalse (success or failure)
  *

ext/mysql2/extconf.rb

@@ -28,7 +28,7 @@ def add_ssl_defines(header)
   end
 end
 
-### Check for Ruby C extention interfaces
+### Check for Ruby C extension interfaces
 
 # 2.1+
 have_func('rb_absint_size')