build: Add -mfloat-abi=softfp on Android

It seems that Android requires `-mfloat-abi=softfp -mfpu=neon` in the
compilation flags in order to use the NEON instructions, even if the
configure time check passes with `-mfpu=neon` alone.

[ebassi/graphene#12]
Add 1.2 version macros

Issue: #16
vectors: Add scalar multiplication

Add an operator that allows multipling all our vector types with a scalar
value.

Issue: #16
docs: Add newly introduced scale() vec operator

Issue: #16
Merge pull request #17 from ebassi/issue/16

Issue/16
matrix: Add point3d transformation

Issue: #18
Merge pull request #19 from ebassi/issues/18

matrix: Add point3d transformation
Merge pull request #20 from ebassi/issues/12

build: Add -mfloat-abi=softfp on Android
build: Check for sed before using $SED
build: Look for NEON intrinsics instead of assembly

We're checking for availability of ARM NEON assembly in order to
determine whether or not we can use NEON instructions; at the same time,
we're not using assembly anywhere, and we're instead relying on the
existence of the NEON intrinsics. There's the chance of false positives
out there — toolchains that only have ARM NEON assembly but no
intrinsics supported — so we need to be more explicit as to what we look
for and use. If, at some point, we'll have assembly versions of the NEON
SIMD implementation then we'll add the assembly check back.
Merge pull request #22 from alexlarsson/master

Add matrix_look_at_testcase
Fix typo in graphene_simd4x4f_inverse

The destination variable is called "...yzwx", but it was multiplying by
wxyz...
Add matrix invert test to verify previous fix