Correct spelling mistakes in doc folder

- OSX —> OS X
- XCode —> Xcode
- github —> GitHub
- homebrew —> Homebrew
- gitian —> Gitian
- Other miscellaneous obvious spelling fixes and whitespace removal

doc/build-osx.md

@@ -1,6 +1,6 @@
 Mac OS X Build Instructions and Notes
 ====================================
-This guide will show you how to build bitcoind (headless client) for OSX.
+This guide will show you how to build bitcoind (headless client) for OS X.
 
 Notes
 -----
@@ -13,8 +13,8 @@ built-in one is located in `/Applications/Utilities`.
 Preparation
 -----------
 
-You need to install XCode with all the options checked so that the compiler
-and everything is available in /usr not just /Developer. XCode should be
+You need to install Xcode with all the options checked so that the compiler
+and everything is available in /usr not just /Developer. Xcode should be
 available on your OS X installation media, but if not, you can get the
 current version from https://developer.apple.com/xcode/. If you install
 Xcode 4.3 or later, you'll need to install its command line tools. This can
@@ -38,7 +38,7 @@ NOTE: Building with Qt4 is still supported, however, could result in a broken UI
 
 ### Building `bitcoind`
 
-1. Clone the github tree to get the source code and go into the directory.
+1. Clone the GitHub tree to get the source code and go into the directory.
 
         git clone https://github.com/bitcoin/bitcoin.git
         cd bitcoin
@@ -62,7 +62,7 @@ Use Qt Creator as IDE
 You can use Qt Creator as IDE, for debugging and for manipulating forms, etc.
 Download Qt Creator from http://www.qt.io/download/. Download the "community edition" and only install Qt Creator (uncheck the rest during the installation process).
 
-1. Make sure you installed everything through homebrew mentioned above 
+1. Make sure you installed everything through Homebrew mentioned above
 2. Do a proper ./configure --with-gui=qt5 --enable-debug
 3. In Qt Creator do "New Project" -> Import Project -> Import Existing Project
 4. Enter "bitcoin-qt" as project name, enter src/qt as location