Adds the initial version of the podspec for the proto3 Objective-C runtime.

Protobuf.podspec

@@ -0,0 +1,23 @@
+Pod::Spec.new do |s|
+  s.name     = 'Protobuf'
+  s.version  = '3.0.0'
+  s.summary  = 'Protocol Buffers v.3 runtime library for Objective-C.'
+  s.homepage = 'https://github.com/google/protobuf'
+  s.license  = 'New BSD'
+  s.authors  = { 'The Protocol Buffers contributors'   => 'protobuf@googlegroups.com' }
+
+  s.source_files = 'objectivec/*.{h,m}', 'objectivec/google/protobuf/*.pbobjc.h', 'objectivec/google/protobuf/Descriptor.pbobjc.m'
+  s.public_header_files = 'objectivec/*.h', 'objectivec/google/protobuf/*.pbobjc.h'
+  # The following is a .m umbrella file, and would cause duplicate symbol
+  # definitions:
+  s.exclude_files = 'objectivec/GPBProtocolBuffers.m'
+  # The .m's of the proto Well-Known-Types under google/protobuf are #imported
+  # by GPBWellKnownTypes.m. So we can't compile them (duplicate symbols), but we
+  # need them available for the importing:
+  s.preserve_paths = 'objectivec/google/protobuf/*.pbobjc.m'
+  s.header_mappings_dir = 'objectivec'
+
+  s.ios.deployment_target = '6.0'
+  s.osx.deployment_target = '10.8'
+  s.requires_arc = false
+end