glad_wgl.c / APIENTRYP : compilation issue in version 1.32 & 1.31
Hi,

In vs2017 c++; with the lastest version of glad (1.32); a compilation issue occurs:

```
glad_wgl.c(90): error C2143: syntax error: missing ')' before '*'
````
Recently  the macro APIENTRY has been undefined by your generator:

```
#if defined(_WIN32) || defined(__CYGWIN__)
#undef APIENTRY    <===============================
#include <windows.h>
static HMODULE libGL;
```

From my side , the version 1.28 is correct; and apprently it's ok up to 1.30 :

```
#if defined(_WIN32) || defined(__CYGWIN__)
#include <windows.h>
static HMODULE libGL;
```
Many thanks

