Import Pdfium API release 6721.

[ajrcarey]

https://github.com/bblanchon/pdfium-binaries/releases

[ajrcarey]

The following functions have changed signatures in pdfium_future:

• fn FPDFPageObjMark_GetName(&self, mark: FPDF_PAGEOBJECTMARK, buffer: *mut FPDF_WCHAR, buflen: c_ulong, out_buflen: *mut c_ulong) -> FPDF_BOOL
• fn FPDFPageObjMark_GetParamKey(&self, mark: FPDF_PAGEOBJECTMARK, index: c_ulong, buffer: *mut FPDF_WCHAR, buflen: c_ulong, out_buflen: *mut c_ulong ) -> FPDF_BOOL;
• fn FPDFPageObjMark_GetParamStringValue(&self, mark: FPDF_PAGEOBJECTMARK, key: &str, buffer: *mut FPDF_WCHAR, buflen: c_ulong, out_buflen: *mut c_ulong ) -> FPDF_BOOL;
• fn FPDFPageObjMark_GetParamBlobValue(&self, mark: FPDF_PAGEOBJECTMARK, key: &str, buffer: *mut c_uchar, buflen: c_ulong, out_buflen: *mut c_ulong ) -> FPDF_BOOL;
• fn FPDFPageObjMark_SetBlobParam(&self, document: FPDF_DOCUMENT, page_object: FPDF_PAGEOBJECT, mark: FPDF_PAGEOBJECTMARK, key: &str, value: *const c_uchar, value_len: c_ulong) -> FPDF_BOOL;

In all cases, it is the buffer (or value) parameter that has changed from a *mut void (or similar) to a more concrete type.

[ajrcarey]

Still need to update README at https://github.com/ajrcarey/pdfium-render#crate-features-for-selecting-pdfium-api-versions