Incorrect values returned on error in CAPI

[dbaston]

In some cases, the CAPI function GEOSLength_r returns 2 on error, when it is documented to return 0. The 2 is likely to be interpreted as "success" by a caller.

In some cases, the CAPI function GEOSIsValidDetail_r returns 0 on error, when it is documented to return 2. The 0 would be falsely interpreted as "geometry invalid."

[dbaston]

PR at ​https://github.com/libgeos/geos/pull/131

[Daniel Baston <dbaston@…>]

In bfe6b8b/git:

Fix incorrect error return values in CAPI

Fixes #941

[Daniel Baston <dbaston@…>]

In 038813ea/git:

Fix incorrect error return values in CAPI

Fixes #941

[Daniel Baston <dbaston@…>]

In d1a649f/git:

Fix incorrect error return values in CAPI

Fixes #941