Fix windows compilation error for alloca.

Added MacOS testing.

.travis.yml

@@ -1,8 +1,33 @@
-sudo: required
-services:
-  - docker
-before_install:
-  - docker pull statusteam/nim-base
-script:
-  - docker run statusteam/nim-base nim --version
-  - docker run -v "$(pwd):/project" -w /project statusteam/nim-base sh -c "nimble install -dy && nimble test"
+matrix:
+  include:
+    - os: linux
+      sudo: required
+      services:
+        - docker
+      before_install:
+        - docker pull statusteam/nim-base
+      script:
+        - docker run statusteam/nim-base nim --version
+        - docker run -v "$(pwd):/project" -w /project statusteam/nim-base sh -c "nimble install -dy && nimble test"
+
+    - os: osx
+      before_install:
+        - git clone https://github.com/nim-lang/nim.git
+        - cd nim
+        - git remote add statusim https://github.com/status-im/nim.git
+        - git fetch statusim
+        - git config --global user.email "you@example.com"
+        - git config --global user.name "Your Name"
+        - for b in $(git branch -a --list 'statusim/status-autopatch-*'); do git merge $b; done
+        - git clone --depth 1 https://github.com/nim-lang/csources.git
+        - cd csources
+        - sh build.sh
+        - cd ..
+        - export PATH=$PWD/bin:$PATH
+        - nim c koch
+        - ./koch boot -d:release
+        - ./koch nimble
+        - cd ..
+
+      script:
+        - nimble install -dy && nimble test  

ranges/stackarrays.nim

@@ -42,7 +42,10 @@ type
     bufferLen: int32
     buffer: UncheckedArray[T]
 
-proc alloca(n: int): pointer {.importc, header: "<alloca.h>".}
+when defined(windows):
+  proc alloca(n: int): pointer {.importc, header: "<malloc.h>".}
+else:
+  proc alloca(n: int): pointer {.importc, header: "<alloca.h>".}
 
 proc raiseRangeError(s: string) =
   raise newException(RangeError, s)
@@ -116,4 +119,3 @@ template toOpenArray*(a: StackArray, first: int): auto =
 template toOpenArray*(a: StackArray, first, last: int): auto =
   if first < 0 or first >= last or last <= a.len: raiseOutOfRange()
   toOpenArray(a.buffer, first, last)
-