Remove external assembly (#343)

Author: Freax13

Cargo.toml

@@ -30,19 +30,18 @@ bit_field = "0.10.1"
 bitflags = "1.0.4"
 volatile = "0.4.4"
 
-[build-dependencies]
-cc = { version = "1.0.37", optional = true }
-
 [features]
 default = [ "nightly", "instructions" ]
 instructions = []
-external_asm = [ "cc" ]
-nightly = [ "inline_asm", "const_fn", "abi_x86_interrupt", "doc_cfg" ]
-inline_asm = []
+nightly = [ "const_fn", "abi_x86_interrupt", "doc_cfg" ]
 abi_x86_interrupt = []
 const_fn = []
 doc_cfg = []
 
+# These features are no longer used and only there for backwards compatibility.
+external_asm = []
+inline_asm = []
+
 [package.metadata.release]
 no-dev-version = true
 pre-release-replacements = [