Bump the minimum Rust version to 1.25

This lets bindgen use `#[repr(align = …)]`, which removes the need
for dummy `__bindgen_align` zero-size array fields.

This field was only present with some versions of libclang (presumably),
which could cause build failures like:

```rust
error[E0560]: struct `generated::root::JS::Value` has no field named `__bindgen_align`sys
  --> /home/simon/projects/mozjs/src/jsval.rs:83:2
   |
83 |     __bindgen_align: [],
   |     ^^^^^^^^^^^^^^^ `generated::root::JS::Value` does not have this field
```

Author: SimonSapin

.travis.yml

@@ -3,6 +3,7 @@ rust:
   - nightly
   - beta
   - stable
+  - 1.25.0
 sudo: 9000
 dist: trusty
 os:

build.rs

@@ -176,7 +176,7 @@ fn build_jsapi_bindings() {
     config &= !bindgen::CodegenConfig::METHODS;
 
     let mut builder = bindgen::builder()
-        .rust_target(bindgen::RustTarget::Stable_1_19)
+        .rust_target(bindgen::RustTarget::Stable_1_25)
         .header("./src/jsglue.hpp")
         // Translate every enum with the "rustified enum" strategy. We should
         // investigate switching to the "constified module" strategy, which has

src/jsval.rs

@@ -79,8 +79,6 @@ const JSVAL_PAYLOAD_MASK: u64 = 0x00007FFFFFFFFFFF;
 #[inline(always)]
 fn AsJSVal(val: u64) -> JSVal {
     JSVal {
-	#[cfg(all(target_os = "android", target_arch = "x86"))]
-	__bindgen_align: [],
         data: Value_layout {
             asBits: val,
         }